Revert "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."

This reverts commit 1c50968


[ROCm/hip commit: 32e11e7dc6]

projects/hip/tests/src/deviceLib/hipDeviceMemcpy.cpp

@@ -16,13 +16,13 @@
 
 __global__ void cpy(hipLaunchParm lp, uint32_t *Out, uint32_t *In)
 {
-    int tx = hipThreadIdx_x;
+    int tx = threadIdx.x;
     memcpy(Out + tx, In + tx, sizeof(uint32_t));
 }
 
 __global__ void set(hipLaunchParm lp, uint32_t *ptr, uint8_t val, size_t size)
 {
-    int tx = hipThreadIdx_x;
+    int tx = threadIdx.x;
     memset(ptr + tx, val, sizeof(uint32_t));
 }