Some minor cleanups:

1. Compute action in X86SelectSelect based on MVT instead of type.
2. Use TLI.getValueType(..) instead of MVT::getVT(..) because the former
   handles pointers and the later doesn't.
3. Don't pass TLI into isTypeLegal, since it already has access to it as 
   an ivar.

#2 gives fast isel some minor new functionality: handling load/stores of
pointers.

llvm-svn: 57552