Revert "drm/amd/display: disable CRTCs with NULL FB on their primary plane (V2)"

This seems to cause flickering and lock-ups for a wide range of users.
Revert until we've found a proper fix for the flickering and lock-ups.

This reverts commit 36cc549d.

Cc: Shirish S <shirish.s@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: NMichel Dänzer <michel.daenzer@amd.com>
Signed-off-by: NHarry Wentland <harry.wentland@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -4848,30 +4848,6 @@ static int dm_update_planes_state(struct dc *dc,
 	return ret;
 }
 
-static int dm_atomic_check_plane_state_fb(struct drm_atomic_state *state,
-					  struct drm_crtc *crtc)
-{
-	struct drm_plane *plane;
-	struct drm_crtc_state *crtc_state;
-
-	WARN_ON(!drm_atomic_get_new_crtc_state(state, crtc));
-
-	drm_for_each_plane_mask(plane, state->dev, crtc->state->plane_mask) {
-		struct drm_plane_state *plane_state =
-			drm_atomic_get_plane_state(state, plane);
-
-		if (IS_ERR(plane_state))
-			return -EDEADLK;
-
-		crtc_state = drm_atomic_get_crtc_state(plane_state->state, crtc);
-		if (crtc->primary == plane && crtc_state->active) {
-			if (!plane_state->fb)
-				return -EINVAL;
-		}
-	}
-	return 0;
-}
-
 static int amdgpu_dm_atomic_check(struct drm_device *dev,
 				  struct drm_atomic_state *state)
 {
@@ -4895,10 +4871,6 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 		goto fail;
 
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
-		ret = dm_atomic_check_plane_state_fb(state, crtc);
-		if (ret)
-			goto fail;
-
 		if (!drm_atomic_crtc_needs_modeset(new_crtc_state) &&
 		    !new_crtc_state->color_mgmt_changed)
 			continue;