OMAPDSS: Remove manager->device references

With the introduction of output entities, managers will now connect to outputs.
Create helper ops for overlays and managers named get_device. This will abstract
away the information on how to get the device from an overlay or an overlay
manager. The get_device ops currently retrieve the output via a
ovl->manager->device reference. This will be later replaced by
ovl->manager->output->device references.

Signed-off-by: Archit Taneja <archit@ti.com>
diff --git a/include/video/omapdss.h b/include/video/omapdss.h
index d8fd1c8..fd8f8be 100644
--- a/include/video/omapdss.h
+++ b/include/video/omapdss.h
@@ -435,6 +435,8 @@
 			struct omap_overlay_info *info);
 
 	int (*wait_for_go)(struct omap_overlay *ovl);
+
+	struct omap_dss_device *(*get_device)(struct omap_overlay *ovl);
 };
 
 struct omap_overlay_manager_info {
@@ -491,6 +493,8 @@
 	int (*apply)(struct omap_overlay_manager *mgr);
 	int (*wait_for_go)(struct omap_overlay_manager *mgr);
 	int (*wait_for_vsync)(struct omap_overlay_manager *mgr);
+
+	struct omap_dss_device *(*get_device)(struct omap_overlay_manager *mgr);
 };
 
 /* 22 pins means 1 clk lane and 10 data lanes */