uapi: Convert some uses of 6 to ETH_ALEN

Use the #define where appropriate.

Add #include <linux/if_ether.h>
where appropriate too.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
index 227d4ce..172a7f0 100644
--- a/include/uapi/linux/virtio_net.h
+++ b/include/uapi/linux/virtio_net.h
@@ -60,7 +60,7 @@
 
 struct virtio_net_config {
 	/* The config defining mac address (if VIRTIO_NET_F_MAC) */
-	__u8 mac[6];
+	__u8 mac[ETH_ALEN];
 	/* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
 	__u16 status;
 	/* Maximum number of each of transmit and receive queues;