RISC-V: Several vector tests fail after JDK-8354383

Hi all,
Please take a look and review this PR, thanks!

After JDK-8354383, the following test cases fail when fastdebug with rvv:
jdk/incubator/vector/Byte128VectorLoadStoreTests.java
jdk/incubator/vector/Byte256VectorLoadStoreTests.java
jdk/incubator/vector/Byte64VectorLoadStoreTests.java
jdk/incubator/vector/ByteMaxVectorLoadStoreTests.java
jdk/incubator/vector/Double128VectorLoadStoreTests.java
jdk/incubator/vector/Double256VectorLoadStoreTests.java
jdk/incubator/vector/DoubleMaxVectorLoadStoreTests.java
jdk/incubator/vector/Float128VectorLoadStoreTests.java
jdk/incubator/vector/Float256VectorLoadStoreTests.java
jdk/incubator/vector/Float64VectorLoadStoreTests.java
jdk/incubator/vector/FloatMaxVectorLoadStoreTests.java
jdk/incubator/vector/Short128VectorLoadStoreTests.java
jdk/incubator/vector/Short256VectorLoadStoreTests.java
jdk/incubator/vector/Short64VectorLoadStoreTests.java
jdk/incubator/vector/ShortMaxVectorLoadStoreTests.java

The error log is as follows:
o531 CastVV === o726 o751 [[ o530 ]] #vectormask<B,8> unconditional dependency

--N: o531 CastVV === o726 o751 [[ o530 ]] #vectormask<B,8> unconditional dependency

   --N: o751 Phi === o726 o539 o293 [[ o531 ]] #vectormask<B,8>
   VREGMASK 0 VREGMASK
   VREGMASK_V0 0 VREGMASK_V0

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/home/zhangdingli/jdk/src/hotspot/share/opto/matcher.cpp:1765), pid=1692890, tid=1693070
# assert(false) failed: bad AD file
#
# JRE version: OpenJDK Runtime Environment (26.0) (fastdebug build 26-internal-adhoc.zhangdingli.jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 26-internal-adhoc.zhangdingli.jdk, mixed mode, compressed oops, compressed class ptrs, g1 gc, linux-riscv64)
# Problematic frame:
# V [libjvm.so+0x10fdfd0] Matcher::Label_Root(Node const*, State*, Node*, Node*&)+0x680
#
# Core dump will be written. Default location: Core dumps may be processed with "/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h" (or dumping to /home/zhangdingli/jdk/jtreg_0708/JTwork/scratch/0/core.1692890)
#
# An error report file with more information is saved as:

The reason for the error is that riscv lacks CastVV with dst as the mask register.