[Vector API] Fix an assert in Assembler::vpmovzxbw if UseAVX=0

# Symptom
```
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/home/jvm/jiefu/docker/jdk/src/hotspot/cpu/x86/assembler_x86.cpp:4263), pid=19129, tid=19145
# Error: assert(vector_len == AVX_128bit? VM_Version::supports_avx() : vector_len == AVX_256bit? VM_Version::supports_avx2() : vector_len == AVX_512bit? VM_Version::supports_avx512bw() : 0) failed
#

Current CompileTask:
C2: 12380 855 b jdk.incubator.vector.ShortMaxVector::rearrange (6 bytes)

Stack: [0x00007f4c095fa000,0x00007f4c096fb000], sp=0x00007f4c096f5d40, free space=1007k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x5e0ab6] Assembler::vpmovzxbw(XMMRegisterImpl*, XMMRegisterImpl*, int)+0x136
V [libjvm.so+0x41d0dd] loadShuffleSNode::emit(CodeBuffer&, PhaseRegAlloc*) const+0x3ad
V [libjvm.so+0x13ea963] PhaseOutput::scratch_emit_size(Node const*)+0x423
V [libjvm.so+0x13e1b44] PhaseOutput::shorten_branches(unsigned int*)+0x2a4
V [libjvm.so+0x13f25aa] PhaseOutput::Output()+0xb8a
V [libjvm.so+0x96a003] Compile::Code_Gen()+0x443
V [libjvm.so+0x97303a] Compile::Compile(ciEnv*, ciMethod*, int, bool, bool, bool, bool, DirectiveSet*)+0x178a
V [libjvm.so+0x7e2a0a] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x10a
V [libjvm.so+0x981136] CompileBroker::invoke_compiler_on_method(CompileTask*)+0xc06
V [libjvm.so+0x981c68] CompileBroker::compiler_thread_loop()+0x468
V [libjvm.so+0x17d56ea] JavaThread::thread_main_inner()+0x2fa
V [libjvm.so+0x17d5a07] JavaThread::run()+0x2b7
V [libjvm.so+0x17da7d8] Thread::call_run()+0xf8
V [libjvm.so+0x13cd67e] thread_native_entry(Thread*)+0x10e
```

# Reproduce
Run jdk/incubator/vector/ShortMaxVectorTests.java with -XX:UseAVX=0