AVX512: Remove VSHRI kmask patterns from TD file. It is incorrect to use...

AVX512: Remove VSHRI kmask patterns from TD file. It is incorrect to use kshiftw to implement VSHRI v4i1 , bits 15-4 is undef so the upper bits of v4i1 may not be zeroed. v4i1 should be zero_extend to v16i1 ( or any natively supported vector).

Differential Revision: http://reviews.llvm.org/D17763

llvm-svn: 262797