drm/virtio: removed optional dummy encoder mode_fixup function.

mode_fixup function for encoder drivers became optional with patch
http://patchwork.freedesktop.org/patch/msgid/1455106522-32307-1-git-send-email-palminha@synopsys.com

This patch set nukes all the dummy mode_fixup implementations.

(made on top of Daniel topic/drm-misc branch)
Signed-off-by: Carlos Palminha <palminha@synopsys.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/85230bc1356eb52257aaa1e1965adae2f00db5cd.1455540137.git.palminha@synopsys.com

drivers/gpu/drm/virtio/virtgpu_display.c

@@ -282,13 +282,6 @@ static const struct drm_crtc_helper_funcs virtio_gpu_crtc_helper_funcs = {
 	.atomic_check  = virtio_gpu_crtc_atomic_check,
 };
 
-static bool virtio_gpu_enc_mode_fixup(struct drm_encoder *encoder,
-				      const struct drm_display_mode *mode,
-				      struct drm_display_mode *adjusted_mode)
-{
-	return true;
-}
-
 static void virtio_gpu_enc_mode_set(struct drm_encoder *encoder,
 				    struct drm_display_mode *mode,
 				    struct drm_display_mode *adjusted_mode)
@@ -362,7 +355,6 @@ virtio_gpu_best_encoder(struct drm_connector *connector)
 }
 
 static const struct drm_encoder_helper_funcs virtio_gpu_enc_helper_funcs = {
-	.mode_fixup = virtio_gpu_enc_mode_fixup,
 	.mode_set   = virtio_gpu_enc_mode_set,
 	.enable     = virtio_gpu_enc_enable,
 	.disable    = virtio_gpu_enc_disable,