[X86] Add a test case showing a bad disassembling of an EVEX instruction with EVEX...

[X86] Add a test case showing a bad disassembling of an EVEX instruction with EVEX.X=0 and a GPR encoded in modrm.rm.

EVEX.X is used to extended modrm.rm when the instruction encodes a XMM/YMM/ZMM register. But we aren't properly ignoring it when it encodes a GPR and we end up printing whatever registers exist in X86 register enum after the GPRs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@333724 91177308-0d34-0410-b5e6-96231b3b80d8