Fix miscompilation of float vector returns. Compile code to this:

Fix miscompilation of float vector returns.  Compile code to this:

_func:
        vsldoi v2, v3, v2, 12
        vsldoi v2, v2, v2, 4
        blr

instead of:

_func:
        vsldoi v2, v3, v2, 12
        vsldoi v2, v2, v2, 4
***     vor f1, v2, v2
        blr

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29607 91177308-0d34-0410-b5e6-96231b3b80d8