Fixed a typo in the test s/CEHCK/CHECK/

Summary:
Turns out the test was not correct, I had to adjust the test to work.  I
also added CHECK-LABELs for better error messages from FileCheck while
I'm here.

Reviewers: jsji

Subscribers: nemanjai, eraman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58614

llvm-svn: 355079