Switch several more Sema Diag methods over. This simplifies the

Switch several more Sema Diag methods over.  This simplifies the
__builtin_prefetch code to only emit one diagnostic per builtin_prefetch.
While this has nothing to do with the rest of the patch, the code seemed
like overkill when I was updating it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59588 91177308-0d34-0410-b5e6-96231b3b80d8