drm/gma500/cdv: Add and hook up chip op for disabling sr

Add a callback hook to the chip ops struct to allow chips to have their
specific self-refresh function. Currently only used by cdv.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
diff --git a/drivers/gpu/drm/gma500/cdv_device.h b/drivers/gpu/drm/gma500/cdv_device.h
index 9e48056..705c11d 100644
--- a/drivers/gpu/drm/gma500/cdv_device.h
+++ b/drivers/gpu/drm/gma500/cdv_device.h
@@ -27,3 +27,4 @@
 extern struct drm_display_mode *cdv_intel_crtc_mode_get(struct drm_device *dev,
 					     struct drm_crtc *crtc);
 extern void cdv_update_wm(struct drm_device *dev, struct drm_crtc *crtc);
+extern void cdv_disable_sr(struct drm_device *dev);