gpu: nvgpu: async cmd resp for gv11b

- When DISALLOW cmd is sent from driver to PMU the actual
  completion of the disallow will be acknowledged by PMU
  via a PG EVENT: ASYNC_CMD_RESP.
- Disallow needs a delayed ACK from PMU in order to disable
  the ELPG.
- If ELPG is already engaged, the DISALLOW cmd will trigger
  ELPG exit and then transition to PMU_PG_STATE_DISALLOW.
- After this whole process is completed, PMU will send
  DISALLOW_ACK through ASYNC_CMD_RESP msg.
- After disallow command is sent from the driver, NvGPU driver
  waits/polls for disallow command ack. This is sent immediately
  by msg framework of PMU.
- Then, the driver will poll/wait for ASYNC_CMD_RESP event which
  is the delayed DISALLOW ACK.
- The driver captures the ASYNC_CMD_RESP sent from PMU.
- set disallow_state to ELPG_OFF.
- If the driver does not wait/poll for this delayed disallow
  ack from PMU, it can result in erros  as PMU is still
  processing DISALLOW cmd but the driver progressed further.

Bug 3580271

Change-Id: I332180c05b6a398107f065d54e9718b7038fb1b2
Signed-off-by: Divya <dsinghatwari@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2689500
Reviewed-by: Sagar Kamble <skamble@nvidia.com>
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-cert <svc-mobile-cert@nvidia.com>
Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com>
GVS: Gerrit_Virtual_Submit

drivers/gpu/nvgpu/common/pmu/pg/pmu_pg.c

@@ -402,7 +402,7 @@ int nvgpu_pmu_disable_elpg(struct gk20a *g)
 		if ((BIT32(pg_engine_id) & pg_engine_id_list) != 0U) {
 			if (pg_engine_id == PMU_PG_ELPG_ENGINE_ID_GRAPHICS) {
 				pmu->pg->elpg_stat = PMU_ELPG_STAT_OFF_PENDING;
-				if (pmu->pg->process_rpc_event != NULL) {
+				if (pmu->pg->process_pg_event != NULL) {
 					pmu->pg->disallow_state =
 						PMU_ELPG_STAT_OFF_PENDING;
 				}
@@ -453,7 +453,7 @@ int nvgpu_pmu_disable_elpg(struct gk20a *g)
 			 * Wait for DISALLOW_ACK RPC event from
 			 * PMU.
 			 */
-			if (pmu->pg->process_rpc_event != NULL) {
+			if (pmu->pg->process_pg_event != NULL) {
 				ptr = &pmu->pg->disallow_state;
 				pmu_wait_message_cond(pmu,
 					nvgpu_get_poll_timeout(g),