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.h

@@ -100,7 +100,4 @@ extern bool gma_pll_is_valid(struct drm_crtc *crtc,
 extern bool gma_find_best_pll(const struct gma_limit_t *limit,
 			      struct drm_crtc *crtc, int target, int refclk,
 			      struct gma_clock_t *best_clock);
-
-/* Cedarview specific functions */
-extern void cdv_intel_disable_self_refresh(struct drm_device *dev);
 #endif