[X86][AVX512] Adding missing shuffle lowering to blend mask instructions 

Some shuffles can be lowered to blend mask instruction (VPBLENDMB/VPBLENDMW/VPBLENDMD/VPBLENDMQ) .
In this patch, I added new pattern match for this case.

Reviewers:
1. craig.topper
2. guyblank
3. RKSimon
4. igorb     

Differential Revision: https://reviews.llvm.org/D28483


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291888 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed