Revert "Set calling convention for CUDA kernel"

This reverts r328795 which introduced an issue with referencing __global__
function templates. More details in the original review D44747.

llvm-svn: 329099
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index e917bcc..dea1c2e 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1481,6 +1481,7 @@
                  .getTypePtr());
       Changed = true;
     }
+
     // Convert FromFPT's ExtParameterInfo if necessary. The conversion is valid
     // only if the ExtParameterInfo lists of the two function prototypes can be
     // merged and the merged list is identical to ToFPT's ExtParameterInfo list.