[AVX512BW] Change truncStore action (v16i16->v16i18). It can be legal only with AVX512VL.

Differential Revision: http://reviews.llvm.org/D24547

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281445 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed