gpu: nvgpu: drop user callback support in CE

Simplify the copyengine code by deleting support for the
ce_event_callback feature that has never been used. Similarly, create a
channel without the finish callback to get rid of that Linux dependency,
and delete the finish callback function as it now serves no purpose.

Delete also the submitted_seq_number and completed_seq_number fields
that are only written to.

Jira NVGPU-259

Change-Id: I02d15bdcb546f4dd8895a6bfb5130caf88a104e2
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1589320
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/common/linux/ce2.c

@@ -173,7 +173,6 @@ int gk20a_ce_execute_ops(struct gk20a *g,
 
 			/* Next available command buffer queue Index */
 			++ce_ctx->cmd_buf_read_queue_offset;
-			++ce_ctx->submitted_seq_number;
 		}
 	} else {
 		ret = -ENOMEM;