drm/exynos: remove exynos_encoder's .commit() op

.commit() is not used anymore, Exynos encoders now follow the
.enable()/.disable() semantics from drm atomic core, so remove this
callback.
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_drv.h

@@ -87,7 +87,6 @@ struct exynos_drm_plane {
  *	      would be called by encoder->mode_set().
  * @enable: display device on.
  * @disable: display device off.
- * @commit: apply changes to hw
  */
 struct exynos_drm_encoder;
 struct exynos_drm_encoder_ops {
@@ -100,7 +99,6 @@ struct exynos_drm_encoder_ops {
 				struct drm_display_mode *mode);
 	void (*enable)(struct exynos_drm_encoder *encoder);
 	void (*disable)(struct exynos_drm_encoder *encoder);
-	void (*commit)(struct exynos_drm_encoder *encoder);
 };
 
 /*

drivers/gpu/drm/exynos/exynos_drm_encoder.c

@@ -56,9 +56,6 @@ static void exynos_drm_encoder_enable(struct drm_encoder *encoder)
 
 	if (exynos_encoder->ops->enable)
 		exynos_encoder->ops->enable(exynos_encoder);
-
-	if (exynos_encoder->ops->commit)
-		exynos_encoder->ops->commit(exynos_encoder);
 }
 
 static void exynos_drm_encoder_disable(struct drm_encoder *encoder)