[MCA][x86][NFC] Add tests for -register-file-stats, -scheduler-stats

Summary:
There does not seem to be any other tests for this.
Split off from D47676.

Reviewers: RKSimon, craig.topper, courbet, andreadb

Reviewed By: andreadb

Subscribers: javed.absar, gbedwell, llvm-commits

Differential Revision: https://reviews.llvm.org/D48190

llvm-svn: 334832