OMAPDSS: DISPC: add dispc_ovl_check()

This patch adds a new function, dispc_ovl_check(), which can be used to
verify scaling configuration for an overlay. The function gets both the
overlay and overlay manager as parameters, so that the caller does not
need to configure the hardware before using this function.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/omap2/dss/dss.h b/drivers/video/omap2/dss/dss.h
index 2754bcb..180b381 100644
--- a/drivers/video/omap2/dss/dss.h
+++ b/drivers/video/omap2/dss/dss.h
@@ -423,6 +423,10 @@
 bool dispc_ovl_enabled(enum omap_plane plane);
 void dispc_ovl_set_channel_out(enum omap_plane plane,
 		enum omap_channel channel);
+int dispc_ovl_check(enum omap_plane plane, enum omap_channel channel,
+		const struct omap_overlay_info *oi,
+		const struct omap_video_timings *timings,
+		int *x_predecim, int *y_predecim);
 
 u32 dispc_mgr_get_vsync_irq(enum omap_channel channel);
 u32 dispc_mgr_get_framedone_irq(enum omap_channel channel);