[x86][inline-asm][clang] accept 'v' constraint

[x86][inline-asm][clang] accept 'v' constraint
Commit on behalf of: Coby Tayree

1.'v' constraint for (x86) non-avx arch imitates the already implemented 'x' constraint, i.e. allows XMM{0-15} & YMM{0-15} depending on the apparent arch & mode (32/64).
2.for the avx512 arch it allows [X,Y,Z]MM{0-31} (mode dependent)

This patch applies the needed changes to clang
LLVM patch: https://reviews.llvm.org/D25005

Differential Revision: https://reviews.llvm.org/D25005

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@285688 91177308-0d34-0410-b5e6-96231b3b80d8