[X86][AVX] Extend hasVEX_WPrefix bit to accept WIG value (W Ignore) + update all...

[X86][AVX] Extend hasVEX_WPrefix bit to accept WIG value (W Ignore) + update all AVX instructions with the new value.

Add WIG value to all of AVX instructions which ignore the W-bit in their encoding, instead of giving them the default value of 0.
This patch is needed for a follow up work on EVEX2VEX pass (replacing EVEX encoded instructions with their corresponding VEX version when possible).

Differential Revision: https://reviews.llvm.org/D29876

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295643 91177308-0d34-0410-b5e6-96231b3b80d8