OMAPDSS: add dispc_ovl_enabled()

Add new dispc function, dispc_ovl_enabled(). This returns if the overlay
enable bit is set in the registers.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/omap2/dss/dispc.c

@@ -2589,6 +2589,11 @@ int dispc_ovl_enable(enum omap_plane plane, bool enable)
 	return 0;
 }
 
+bool dispc_ovl_enabled(enum omap_plane plane)
+{
+	return REG_GET(DISPC_OVL_ATTRIBUTES(plane), 0, 0);
+}
+
 static void dispc_mgr_disable_isr(void *data, u32 mask)
 {
 	struct completion *compl = data;

drivers/video/omap2/dss/dss.h

@@ -427,6 +427,7 @@ int dispc_ovl_setup(enum omap_plane plane, const struct omap_overlay_info *oi,
 		bool replication, const struct omap_video_timings *mgr_timings,
 		bool mem_to_mem);
 int dispc_ovl_enable(enum omap_plane plane, bool enable);
+bool dispc_ovl_enabled(enum omap_plane plane);
 void dispc_ovl_set_channel_out(enum omap_plane plane,
 		enum omap_channel channel);