drm/omap: Remove unneeded safety checks in the HPD operations

The HPD-related omap_dss_device operations are now only called when the
device supports HPD. There's no need to duplicate that check in the
omap_dss_device drivers. The .register_hpd_cb() operation can as a
result be turned into a void operation.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/omapdss.h

@@ -372,10 +372,10 @@ struct omap_dss_device_ops {
 
 	bool (*detect)(struct omap_dss_device *dssdev);
 
-	int (*register_hpd_cb)(struct omap_dss_device *dssdev,
-			       void (*cb)(void *cb_data,
+	void (*register_hpd_cb)(struct omap_dss_device *dssdev,
+				void (*cb)(void *cb_data,
 					  enum drm_connector_status status),
-			       void *cb_data);
+				void *cb_data);
 	void (*unregister_hpd_cb)(struct omap_dss_device *dssdev);
 	void (*enable_hpd)(struct omap_dss_device *dssdev);
 	void (*disable_hpd)(struct omap_dss_device *dssdev);