drm: arcpgu: arc_pgu_crtc_mode_valid() can be static

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170623095418.GA68865@lkp-sbx04

drivers/gpu/drm/arc/arcpgu_crtc.c

@@ -64,7 +64,7 @@ static const struct drm_crtc_funcs arc_pgu_crtc_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
 };
 
-enum drm_mode_status arc_pgu_crtc_mode_valid(struct drm_crtc *crtc,
+static enum drm_mode_status arc_pgu_crtc_mode_valid(struct drm_crtc *crtc,
 						    const struct drm_display_mode *mode)
 {
 	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);