Revert "[mips] Honour -mno-odd-spreg for vector splat"

This reverts commit r291556. It was a mixture of two differentials and
was missing a test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291562 91177308-0d34-0410-b5e6-96231b3b80d8