rocr: Put back scratch_backing_memory_byte_size

The scratch_backing_memory_byte_size is not used by CP, but it is
currently used by rocgdb. Putting the field back, but we need to find a
solution for alt_scratch_backing_memory_byte_size.

Also, completely disabling alternate scratch as we need some changes to
support debugger.

runtime/hsa-runtime/inc/amd_hsa_queue.h

@@ -133,7 +133,7 @@ typedef struct AMD_QUEUE_ALIGN amd_queue_v2_s {
   uint32_t compute_tmpring_size;
   uint32_t scratch_resource_descriptor[4];
   uint64_t scratch_backing_memory_location;
-  uint32_t reserved3[2];
+  uint64_t scratch_backing_memory_byte_size;
   uint32_t scratch_wave64_lane_byte_size;
   amd_queue_properties32_t queue_properties;
   volatile uint64_t scratch_max_use_index;       /* V2 */