drm/i915/overlay: Make do_put_image() as static

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_overlay.c

@@ -689,7 +689,7 @@ static u32 overlay_cmd_reg(struct put_image_params *params)
 	return cmd;
 }
 
-int intel_overlay_do_put_image(struct intel_overlay *overlay,
+static int intel_overlay_do_put_image(struct intel_overlay *overlay,
 				      struct drm_gem_object *new_bo,
 				      struct put_image_params *params)
 {