[FastISel] fix a fallback diagnostic.

Summary: FastISel was marked as failed in case instruction selection succeeded.

Reviewers: qcolombet, zvi, rovka, ab

Reviewed By: zvi

Subscribers: javed.absar, ab, qcolombet, bogner, llvm-commits

Differential Revision: https://reviews.llvm.org/D34438

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307489 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed