drm/rockchip: Rely on the default best_encoder() behavior

Since the output has 1:1 relationship between connectors and encoders,
and the driver is relying on the atomic helpers, remove the custom
best_encoder() and let the core call drm_atomic_helper_best_encoder().
Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20170927182317.GA8249@Haneen

drivers/gpu/drm/rockchip/cdn-dp-core.c

@@ -287,14 +287,6 @@ static int cdn_dp_connector_get_modes(struct drm_connector *connector)
 	return ret;
 }
 
-static struct drm_encoder *
-cdn_dp_connector_best_encoder(struct drm_connector *connector)
-{
-	struct cdn_dp_device *dp = connector_to_dp(connector);
-
-	return &dp->encoder;
-}
-
 static int cdn_dp_connector_mode_valid(struct drm_connector *connector,
 				       struct drm_display_mode *mode)
 {
@@ -346,7 +338,6 @@ static int cdn_dp_connector_mode_valid(struct drm_connector *connector,
 
 static struct drm_connector_helper_funcs cdn_dp_connector_helper_funcs = {
 	.get_modes = cdn_dp_connector_get_modes,
-	.best_encoder = cdn_dp_connector_best_encoder,
 	.mode_valid = cdn_dp_connector_mode_valid,
 };