[AVX512][inline-asm] Fix AVX512 inline assembly instruction resolution when...

[AVX512][inline-asm] Fix AVX512 inline assembly instruction resolution when the size qualifier of a memory operand is not specified explicitly.

This commit handles cases where the size qualifier of an indirect memory reference operand in Intel syntax is missing (e.g. "vaddps xmm1, xmm2, [a]").

GCC will deduce the size qualifier for AVX512 vector and broadcast memory operands based on the possible matches:
"vaddps xmm1, xmm2, [a]" matches only “XMMWORD PTR” qualifier.
"vaddps xmm1, xmm2, [a]{1to4}" matches only “DWORD PTR” qualifier.

This is different from the current behavior of LLVM, which deduces the size qualifier based on the size of the memory operand.
For "vaddps xmm1, xmm2, [a]"
"char a;" will imply "BYTE PTR" qualifier
"short a;" will imply "WORD PTR" qualifier.

This commit aligns LLVM to GCC’s behavior.

This is the LLVM part of the review.
The Clang part of the review: https://reviews.llvm.org/D26587

Differential Revision: https://reviews.llvm.org/D26586

llvm-svn: 287630