Merge commit e6bb4c8e7 from llvm git (by Craig Topper):

[X86] SSE4_A should only imply SSE3 not SSSE3 in the frontend.

SSE4_1 and SSE4_2 due imply SSSE3. So I guess I got confused when
switching the code to being table based in D83273.

Fixes PR47464

This should fix builds with -march=amdfam10 emitting SSSE3 instructions
such as pshufb, which lead to programs crashing with SIGILL on such
processors.

Reported by: avg
MFC after: 6 weeks
X-MFC-With: r364284