Follow up to r289732: Update comments in source files to reference .cpp files

Patch by Hansang Bae

llvm-svn: 289739
diff --git a/openmp/runtime/src/kmp_gsupport.cpp b/openmp/runtime/src/kmp_gsupport.cpp
index e07c09d..2c6d097 100644
--- a/openmp/runtime/src/kmp_gsupport.cpp
+++ b/openmp/runtime/src/kmp_gsupport.cpp
@@ -1,5 +1,5 @@
 /*
- * kmp_gsupport.c
+ * kmp_gsupport.cpp
  */