[SystemZ] Fix commit message of previous commit.

Sorry, the commit comment for r332703 is completely broken.
My mind slipped - the right description would be:

In SystemZDAGToDAGISel::Select(), in the handling for SELECT_CCMASK:

Check if UpdateNodeOperands() returns a different SDNode and in that
case call ReplaceNode.

Review: Ulrich Weigand.
llvm-svn: 332706