[X86] Fix a bug where the disassembler was ignoring the VEX.W bit in 32-bit mode...

[X86] Fix a bug where the disassembler was ignoring the VEX.W bit in 32-bit mode for certain instructions it shouldn't.

Unfortunately, this isn't easy to fix since there's no simple way to figure out from the disassembler tables whether the W-bit is being used to select a 64-bit GPR or if its a required part of the opcode. The fix implemented here just looks for "64" in the instruction name and ignores the W-bit in 32-bit mode if its present.

Fixes PR21169.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219194 91177308-0d34-0410-b5e6-96231b3b80d8