OMAPDSS: remove declarations for non-existing functions

Remove dispc_mgr_is_channel_enabled() and dss_mgr_get_timings()
declarations, as the function doesn't exist.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/omap2/dss/dss.h

@@ -197,7 +197,6 @@ void dss_mgr_set_timings(struct omap_overlay_manager *mgr,
 		const struct omap_video_timings *timings);
 void dss_mgr_set_lcd_config(struct omap_overlay_manager *mgr,
 		const struct dss_lcd_mgr_config *config);
-const struct omap_video_timings *dss_mgr_get_timings(struct omap_overlay_manager *mgr);
 
 bool dss_ovl_is_enabled(struct omap_overlay *ovl);
 int dss_ovl_enable(struct omap_overlay *ovl);
@@ -444,7 +443,6 @@ void dispc_mgr_enable(enum omap_channel channel, bool enable);
 bool dispc_mgr_is_enabled(enum omap_channel channel);
 void dispc_mgr_enable_sync(enum omap_channel channel);
 void dispc_mgr_disable_sync(enum omap_channel channel);
-bool dispc_mgr_is_channel_enabled(enum omap_channel channel);
 void dispc_mgr_set_lcd_config(enum omap_channel channel,
 		const struct dss_lcd_mgr_config *config);
 void dispc_mgr_set_timings(enum omap_channel channel,