drm/vkms: Use simple encoder

The vkms driver uses an empty implementation for its encoder. Replace
the code with the generic simple encoder.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305155950.2705-21-tzimmermann@suse.de

drivers/gpu/drm/vkms/vkms_output.c

@@ -3,6 +3,7 @@
 #include "vkms_drv.h"
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_probe_helper.h>
+#include <drm/drm_simple_kms_helper.h>
 
 static void vkms_connector_destroy(struct drm_connector *connector)
 {
@@ -17,10 +18,6 @@ static const struct drm_connector_funcs vkms_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static const struct drm_encoder_funcs vkms_encoder_funcs = {
-	.destroy = drm_encoder_cleanup,
-};
-
 static int vkms_conn_get_modes(struct drm_connector *connector)
 {
 	int count;
@@ -70,8 +67,7 @@ int vkms_output_init(struct vkms_device *vkmsdev, int index)
 
 	drm_connector_helper_add(connector, &vkms_conn_helper_funcs);
 
-	ret = drm_encoder_init(dev, encoder, &vkms_encoder_funcs,
-			       DRM_MODE_ENCODER_VIRTUAL, NULL);
+	ret = drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_VIRTUAL);
 	if (ret) {
 		DRM_ERROR("Failed to init encoder\n");
 		goto err_encoder;