drm: omapdrm: omap_crtc_flush() isn't called with modeset locked

When performing asynchronous atomic updates the modeset lock isn't taken
around the callers of omap_crtc_flush(). This isn't an issue though, as
access to the CRTC is properly serialized. Just drop the warning.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/omap_crtc.c

@@ -365,7 +365,6 @@ static int omap_crtc_flush(struct drm_crtc *crtc)
 
 	DBG("%s: GO", omap_crtc->name);
 
-	WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
 	WARN_ON(omap_crtc->vblank_irq.registered);
 
 	if (dispc_mgr_is_enabled(omap_crtc->channel)) {