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>

drivers/gpu/drm/gma500/gma_display.c

@@ -211,7 +211,7 @@ void gma_crtc_dpms(struct drm_crtc *crtc, int mode)
 	 */
 
 	if (IS_CDV(dev))
-		cdv_intel_disable_self_refresh(dev);
+		dev_priv->ops->disable_sr(dev);
 
 	switch (mode) {
 	case DRM_MODE_DPMS_ON: