drm/komeda: Potential error pointer dereference

We need to check whether drm_atomic_get_crtc_state() returns an error
pointer before dereferencing "crtc_st".

Fixes: 9e560309 ("drm/komeda: Add komeda_plane/plane_helper_funcs")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: "james qian wang (Arm Technology China)" <james.qian.wang@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>

drivers/gpu/drm/arm/display/komeda/komeda_plane.c

@@ -63,7 +63,7 @@ komeda_plane_atomic_check(struct drm_plane *plane,
 		return 0;
 
 	crtc_st = drm_atomic_get_crtc_state(state->state, state->crtc);
-	if (!crtc_st->enable) {
+	if (IS_ERR(crtc_st) || !crtc_st->enable) {
 		DRM_DEBUG_ATOMIC("Cannot update plane on a disabled CRTC.\n");
 		return -EINVAL;
 	}