drm/rockchip: Convert to using __drm_atomic_helper_crtc_reset() for reset.

Convert rockchip to using __drm_atomic_helper_crtc_reset(), instead of
writing its own version. Instead of open coding
destroy_state(), call it directly for freeing the old state.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Sandy Huang <hjc@rock-chips.com>
Cc: "Heiko Stübner" <heiko@sntech.de>
Cc: linux-rockchip@lists.infradead.org
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20190301125627.7285-14-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/rockchip/rockchip_drm_vop.c

@@ -1210,17 +1210,6 @@ static void vop_crtc_destroy(struct drm_crtc *crtc)
 	drm_crtc_cleanup(crtc);
 }
 
-static void vop_crtc_reset(struct drm_crtc *crtc)
-{
-	if (crtc->state)
-		__drm_atomic_helper_crtc_destroy_state(crtc->state);
-	kfree(crtc->state);
-
-	crtc->state = kzalloc(sizeof(struct rockchip_crtc_state), GFP_KERNEL);
-	if (crtc->state)
-		crtc->state->crtc = crtc;
-}
-
 static struct drm_crtc_state *vop_crtc_duplicate_state(struct drm_crtc *crtc)
 {
 	struct rockchip_crtc_state *rockchip_state;
@@ -1242,6 +1231,17 @@ static void vop_crtc_destroy_state(struct drm_crtc *crtc,
 	kfree(s);
 }
 
+static void vop_crtc_reset(struct drm_crtc *crtc)
+{
+	struct rockchip_crtc_state *crtc_state =
+		kzalloc(sizeof(*crtc_state), GFP_KERNEL);
+
+	if (crtc->state)
+		vop_crtc_destroy_state(crtc, crtc->state);
+
+	__drm_atomic_helper_crtc_reset(crtc, &crtc_state->base);
+}
+
 #ifdef CONFIG_DRM_ANALOGIX_DP
 static struct drm_connector *vop_get_edp_connector(struct vop *vop)
 {