[Hexagon] Only process bitcasts of vsplats when selecting const vectors

Selecting of constant HVX vectors involves some "manual processing",
which mishandled an unrelated BITCAST operation causing a selection
error.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323887 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed