[X86] Update test cases to make sure storeu builtins use the storeu...

[X86] Update test cases to make sure storeu builtins use the storeu instrinsics. We were previously matching on other stores in the IR from this being an -O0 test.

We should probably look into making the storeu builtins just emit a normal store with an alignment of 1.

llvm-svn: 270664