OMAPDSS: add omap_dss_find_output()

Add a support function to find a DSS output by given name. This is used
in later patches to link the panels to DSS outputs.

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

include/video/omapdss.h

@@ -780,6 +780,7 @@ int omap_dss_get_num_overlays(void);
 struct omap_overlay *omap_dss_get_overlay(int num);
 
 struct omap_dss_output *omap_dss_get_output(enum omap_dss_output_id id);
+struct omap_dss_output *omap_dss_find_output(const char *name);
 int omapdss_output_set_device(struct omap_dss_output *out,
 		struct omap_dss_device *dssdev);
 int omapdss_output_unset_device(struct omap_dss_output *out);