gpu: nvgpu: ensure worker thread is disabled during rg

A previous commit ID 44b6bfbc1 added a hack to prevent
the worker thread from calling nvgpu_runlist_tick()
in post_process if the next domain matches the previous.

This could potentially still face issues with multi-domains
in future.

A better way is to synchronize the thread to suspend/resume
alongwith the device's common OS agnostic suspend/resume
operations. This shall emulate the GSP as well.
This shall also take care of the power constraints
i.e. the worker thread can be expected to always work
with the power enabled and thus we can get rid of the complex
gk20a_busy() lock here for good.

Implemented a state-machine based approach for suspending/
resuming the NVS worker thread from the existing callbacks.

Remove support for NVS worker thread creation for VGPU.
hw_submit method is currently set to NULL for VGPU. VGPU
instead submits its updates via the runlist.reload() method.

Jira NVGPU-8609

Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Change-Id: I51a20669e02bf6328dfe5baa122d5bfb75862ea2
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2750403
Reviewed-by: Prateek Sethi <prsethi@nvidia.com>
Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>

drivers/gpu/nvgpu/common/init/nvgpu_init.c

@@ -313,6 +313,9 @@ int nvgpu_prepare_poweroff(struct gk20a *g)
 		}
 	}
 
+	/* Ensure that thread is paused before Engines suspend below */
+	nvgpu_nvs_worker_pause(g);
+
 #ifdef CONFIG_NVGPU_LS_PMU
 	/* disable elpg before gr or fifo suspend */
 	if (g->support_ls_pmu) {