blk: Introduce IF_TYPE_VIRTIO

This adds a new block interface type for VirtIO block devices.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/blk.h

@@ -33,6 +33,7 @@ enum if_type {
 	IF_TYPE_HOST,
 	IF_TYPE_NVME,
 	IF_TYPE_EFI,
+	IF_TYPE_VIRTIO,
 
 	IF_TYPE_COUNT,			/* Number of interface types */
 };