ExpandUnalignedLoad doesn't handle vectors right at all apparently.

Fix a couple of problems:
1. Don't assume the VT-1 is a VT that is half the size.
2. Treat vectors of FP in the vector path, not the FP path.

This has a couple of remaining problems before it will work with
the code in PR1811: the code below this change assumes that it can
use extload/shift/or to construct the result, which isn't right for
vectors.

This also doesn't handle vectors of 1 or vectors that aren't pow-2.

llvm-svn: 44243