[X86] Don't use aligned load/store instructions for fp128 if the load/store isn't...

[X86] Don't use aligned load/store instructions for fp128 if the load/store isn't aligned.

Similarily, don't fold fp128 loads into SSE instructions if the load isn't aligned. Unless we're targeting an AMD CPU that doesn't check alignment on arithmetic instructions.

Should fix PR38001

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336121 91177308-0d34-0410-b5e6-96231b3b80d8