[Hexagon] Use V6_vmpyih for halfword multiplication

Unlike V6_vmpyhv, it produces the result in the exact form that is
expected without the need for a shuffle.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324241 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed