OMAPDSS: export dss_get_def_display_name()

Export dss_get_def_display_name() with the name of
omapdss_get_def_display_name() so that omapfb can use it after the next
patch which moves default display handling to omapfb.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

include/video/omapdss.h

@@ -753,6 +753,7 @@ void omap_dss_put_device(struct omap_dss_device *dssdev);
 struct omap_dss_device *omap_dss_get_next_device(struct omap_dss_device *from);
 struct omap_dss_device *omap_dss_find_device(void *data,
 		int (*match)(struct omap_dss_device *dssdev, void *data));
+const char *omapdss_get_default_display_name(void);
 
 int omap_dss_start_device(struct omap_dss_device *dssdev);
 void omap_dss_stop_device(struct omap_dss_device *dssdev);