drm/radeon: Remove deprecated create_singlethread_workqueue

alloc_workqueue replaces deprecated create_singlethread_workqueue().

Each hardware CRTC has a single flip work queue.
When a radeon_flip_work_func item is queued, it needs to be executed
ASAP because even a slight delay may cause the flip to be delayed by
one refresh cycle.

Hence, a dedicated workqueue with WQ_HIGHPRI set, has been used here
since a delay can cause the outcome to miss the refresh cycle.

Since there are only a fixed number of work items, explicit concurrency
limit is unnecessary here.
Reviewed-by: NChristian König <christian.koenig@amd.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NBhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_display.c

@@ -714,7 +714,7 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
 
 	drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
 	radeon_crtc->crtc_id = index;
-	radeon_crtc->flip_queue = create_singlethread_workqueue("radeon-crtc");
+	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
 	rdev->mode_info.crtcs[index] = radeon_crtc;
 
 	if (rdev->family >= CHIP_BONAIRE) {