drm/virtgpu: Use simple encoder

The virtgpu 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/20200305155950.2705-20-tzimmermann@suse.de

drivers/gpu/drm/virtio/virtgpu_display.c

@@ -30,6 +30,7 @@
 #include <drm/drm_fourcc.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_probe_helper.h>
+#include <drm/drm_simple_kms_helper.h>
 
 #include "virtgpu_drv.h"
 
@@ -240,10 +241,6 @@ static const struct drm_connector_funcs virtio_gpu_connector_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
 };
 
-static const struct drm_encoder_funcs virtio_gpu_enc_funcs = {
-	.destroy = drm_encoder_cleanup,
-};
-
 static int vgdev_output_init(struct virtio_gpu_device *vgdev, int index)
 {
 	struct drm_device *dev = vgdev->ddev;
@@ -276,8 +273,7 @@ static int vgdev_output_init(struct virtio_gpu_device *vgdev, int index)
 	if (vgdev->has_edid)
 		drm_connector_attach_edid_property(connector);
 
-	drm_encoder_init(dev, encoder, &virtio_gpu_enc_funcs,
-			 DRM_MODE_ENCODER_VIRTUAL, NULL);
+	drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_VIRTUAL);
 	drm_encoder_helper_add(encoder, &virtio_gpu_enc_helper_funcs);
 	encoder->possible_crtcs = 1 << index;