[FastISel][AArch64] Add missing test case for previous commit.

This adds the missing test case for the previous commit:
Allow handling of vectors during return lowering for little endian machines.

Sorry for the noise.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217847 91177308-0d34-0410-b5e6-96231b3b80d8