gpu:nvgpu: fix below issue with ctrl nvs.

- Move queue lock at correct place.
- Free the allocated memory.

Jira NVGPU-8622

Change-Id: Ia996d80498e53fb21ddf1f1202abd6fb8e3f6168
Signed-off-by: prsethi <prsethi@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2791618
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svcacv <svcacv@nvidia.com>
Reviewed-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-by: Ankur Kishore <ankkishore@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>

drivers/gpu/nvgpu/os/linux/dmabuf_nvs.c

@@ -85,6 +85,7 @@ static int nvs_release_user_mappings_locked(struct gk20a *g, struct nvgpu_nvs_li
 
 		zap_vma_entries(g, vma);
 		linux_buf->mapped_ref--;
+		nvgpu_kfree(g, current_entry);
 	}
 
 	return err;