video: Support virtio devices with the splash screen

This is useful for showing a logo when booting from qemu.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/splash.h b/include/splash.h
index 7fd2de8..33e45e6 100644
--- a/include/splash.h
+++ b/include/splash.h
@@ -30,6 +30,7 @@
 	SPLASH_STORAGE_MMC,
 	SPLASH_STORAGE_USB,
 	SPLASH_STORAGE_SATA,
+	SPLASH_STORAGE_VIRTIO,
 };
 
 enum splash_flags {