[X86] Use __m128_u for _mm_loadu_ps after r353555

Add secondary triple to existing SSE test for it.  I audited other uses
of __attribute__((__packed__)) in the intrinsic headers, and this seemed
to be the only missing one.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@353878 91177308-0d34-0410-b5e6-96231b3b80d8