Revert adoption of CUDA indexing in general - this can only work with later versions of the compiler, just like module based dispatch, and thus must be guarded against usage in earlier (e.g. 1.6) versions.

tests/src/runtimeApi/module/hipModule.cpp

@@ -34,7 +34,7 @@ THE SOFTWARE.
 #define kernel_name "hello_world"
 
 __global__ void Cpy(hipLaunchParm lp, float *Ad, float* Bd){
-  int tx = threadIdx.x;
+  int tx = hipThreadIdx_x;
   Bd[tx] = Ad[tx];
 }