drm: make drm_mode_object_find typesafe

I've wasted half a day hunting a bug that could easily be spotted by
gcc. Prevent this from reoccurring.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 5cae0b3..ee0cde1 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -247,7 +247,8 @@
 	mutex_unlock(&dev->mode_config.idr_mutex);
 }
 
-void *drm_mode_object_find(struct drm_device *dev, uint32_t id, uint32_t type)
+struct drm_mode_object *drm_mode_object_find(struct drm_device *dev,
+		uint32_t id, uint32_t type)
 {
 	struct drm_mode_object *obj = NULL;
 
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index b69347b..bfcc60d 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -711,7 +711,8 @@
 					   struct drm_encoder *encoder);
 extern bool drm_mode_crtc_set_gamma_size(struct drm_crtc *crtc,
 					 int gamma_size);
-extern void *drm_mode_object_find(struct drm_device *dev, uint32_t id, uint32_t type);
+extern struct drm_mode_object *drm_mode_object_find(struct drm_device *dev,
+		uint32_t id, uint32_t type);
 /* IOCTLs */
 extern int drm_mode_getresources(struct drm_device *dev,
 				 void *data, struct drm_file *file_priv);