Now that we have a canonical way to handle 256-bit splats:

Now that we have a canonical way to handle 256-bit splats:
vinsertf128 $1 + vpermilps $0, remove the old code that used to first
do the splat in a 128-bit vector and then insert it into a larger one.
This is better because the handling code gets simpler and also makes a
better room for the upcoming vbroadcast!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137807 91177308-0d34-0410-b5e6-96231b3b80d8