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

[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.

llvm-svn: 333724