[PPC64LE] Add test case for r210282 commit

Chandler correctly pointed out that I need an LLVM IR test for
r210282, which modified the vperm -> shuffle transform for little
endian PowerPC.  This patch provides that test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210297 91177308-0d34-0410-b5e6-96231b3b80d8