efi_loader: GOP fix for no display

uclass_first_device() returns 0 if there is no device, but error if
there is a device that failed to probe.

Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_loader/efi_gop.c

@@ -137,7 +137,7 @@ int efi_gop_register(void)
 	struct udevice *vdev;
 
 	/* We only support a single video output device for now */
-	if (uclass_first_device(UCLASS_VIDEO, &vdev))
+	if (uclass_first_device(UCLASS_VIDEO, &vdev) || !vdev)
 		return -1;
 
 	struct video_priv *priv = dev_get_uclass_priv(vdev);