[X86][SSE] Add combine tests for PMULDQ/PMULUDQ

Found several missed optimizations while investigating replacing _mm_mul_epi32/_mm_mul_epu32 with generic implementations

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306302 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed