riscv: Fix MachNode size mismatch for MacroAssembler::verify_oops*

Same as JDK-8283737: in fastdebug build, MacroAssembler::verify_oop is used in match rules encodeHeapOop and decodeHeapOop, which also requires a fixed length.

Could be reproduced by -XX:+VerifyOops:

> jdk/bin/java -XX:+VerifyOops -jar demo-0.0.1-SNAPSHOT.jar
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=/output.cpp:1780
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/jdk19/src/hotspot/share/opto/output.cpp:1780), pid=437, tid=452
# guarantee((int)(blk_starts[i+1] - blk_starts[i]) >= (current_offset - blk_offset)) failed: shouldn't increase block size
#
# JRE version: OpenJDK Runtime Environment (19.0) (fastdebug build 19-internal-adhoc..jdk19)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 19-internal-adhoc..jdk19, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-riscv64)
# Problematic frame:
# V [libjvm.so+0xf93f04] PhaseOutput::fill_buffer(CodeBuffer*, unsigned int*)+0x19c0
#
# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /jdk19/hs_err_pid437.log
#
# Compiler replay data is saved as:
# /jdk19/replay_pid437.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
Aborted



> jdk/bin/java -XX:+VerifyOops -jar demo-0.0.1-SNAPSHOT.jar
 2277 decodeHeapOop === _ 2278 [[ 2298 ]] jdk/internal/ref/CleanerImpl:exact * Oop:jdk/internal/ref/CleanerImpl:exact * !jvms: JarFile::<init> @ bci:5 (line 117) JarURLConnection::get @ bci:183 (line 269)
decode_heap_oop R7, R7 #@decodeHeapOop n_size (72), current_offset (4420), instr_offset (4344)
--------------------------------------------------------------------------------
BFD: unrecognized disassembler option:
  0x00000040137a3cb8: slli t2,t2,0x3
  0x00000040137a3cbc: addi sp,sp,-32
  0x00000040137a3cc0: sd ra,0(sp)
  0x00000040137a3cc4: sd t0,8(sp)
  0x00000040137a3cc8: sd t1,16(sp)
  0x00000040137a3ccc: sd a0,24(sp)
  0x00000040137a3cd0: mv a0,t2
  0x00000040137a3cd4: lui t0,0x2094
  0x00000040137a3cd8: addiw t0,t0,467
  0x00000040137a3cdc: slli t0,t0,0xd
  0x00000040137a3ce0: addi t0,t0,-1680 # 0x0000000002093970
  0x00000040137a3ce4: auipc t1,0xef9ca
  0x00000040137a3ce8: ld t1,124(t1) # 0x000000400316dd60
  0x00000040137a3cec: jalr t1
  0x00000040137a3cf0: ld ra,0(sp)
  0x00000040137a3cf4: ld t0,8(sp)
  0x00000040137a3cf8: ld t1,16(sp)
  0x00000040137a3cfc: ld a0,24(sp)
  0x00000040137a3d00: addi sp,sp,32
  0x00000040137a3d04: Address 0x00000040137a3d04 is out of bounds.
--------------------------------------------------------------------------------
 -------------------
--------------------------------------------------------------------------------
BFD: unrecognized disassembler option:
  0x00000040137d2d40: slli t2,t2,0x3
  0x00000040137d2d44: addi sp,sp,-32
  0x00000040137d2d48: sd ra,0(sp)
  0x00000040137d2d4c: sd t0,8(sp)
  0x00000040137d2d50: sd t1,16(sp)
  0x00000040137d2d54: sd a0,24(sp)
  0x00000040137d2d58: mv a0,t2
  0x00000040137d2d5c: lui t0,0x4128
  0x00000040137d2d60: addiw t0,t0,2015
  0x00000040137d2d64: slli t0,t0,0xc
  0x00000040137d2d68: auipc t1,0xef99b
  0x00000040137d2d6c: ld t1,-8(t1) # 0x000000400316dd60
  0x00000040137d2d70: jalr t1
  0x00000040137d2d74: ld ra,0(sp)
  0x00000040137d2d78: ld t0,8(sp)
  0x00000040137d2d7c: ld t1,16(sp)
  0x00000040137d2d80: ld a0,24(sp)
  0x00000040137d2d84: addi sp,sp,32
  0x00000040137d2d88: Address 0x00000040137d2d88 is out of bounds.
--------------------------------------------------------------------------------
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=/output.cpp:1704
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/jdk19/src/hotspot/share/opto/output.cpp:1704), pid=467, tid=497
# assert(false) failed: wrong size of mach node
#
# JRE version: OpenJDK Runtime Environment (19.0) (fastdebug build 19-internal-adhoc..jdk19)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 19-internal-adhoc..jdk19, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-riscv64)
# Problematic frame:
# V [libjvm.so+0xf93488] PhaseOutput::fill_buffer(CodeBuffer*, unsigned int*)+0xf44
#
# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /jdk19/hs_err_pid467.log
#
# Compiler replay data is saved as:
# /jdk19/replay_pid467.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
Aborted