Temporarily comment out Hcc-specific APIs for CLang compiler

Temporarily comment out Hcc-specific template functions
hipExtLaunchKernelGGL and hipOccupancyMaxPotentialBlockSize for CLang
compiler so that all test cases under hip/samples can be built
successfully for Clang + Hip/Hcc runtime.

Change-Id: Iafc761257be4a7b34eafa6759a01f369570cd6ce

samples/1_Utils/hipDispatchLatency/hipDispatchLatency.cpp

@@ -109,7 +109,7 @@ int main() {
     /***********************************************************************************/
 
     //Timing directly the dispatch
-#ifdef __HIP_PLATFORM_HCC__
+#if defined(__HIP_PLATFORM_HCC__) && GENERIC_GRID_LAUNCH == 1 && defined(__HCC__)
     for (auto i = 0; i < TOTAL_RUN_COUNT; ++i) {
         hipExtLaunchKernelGGL((EmptyKernel), dim3(NUM_GROUPS), dim3(GROUP_SIZE), 0, stream0, start, stop, 0);
         hipEventSynchronize(stop);