Fix hipMalloc to return error code if allocation fails.

include/hip/hcc_detail/hip_runtime_api.h

@@ -863,7 +863,7 @@ hipError_t hipPointerGetAttributes(hipPointerAttribute_t *attributes, const void
  *
  *  If size is 0, no memory is allocated, *ptr returns nullptr, and hipSuccess is returned.
  *
- *  @return #hipSuccess
+ *  @return #hipSuccess, #hipErrorMemoryAllocation, #hipErrorInvalidValue (bad context, null *ptr)
  *
  *  @see hipMallocPitch, hipFree, hipMallocArray, hipFreeArray, hipMalloc3D, hipMalloc3DArray, hipHostFree, hipHostMalloc
  */