net: virtio: use eth_hw_addr_set()

Commit 406f42fa0d3c ("net-next: When a bond have a massive amount
of VLANs...") introduced a rbtree for faster Ethernet address look
up. To maintain netdev->dev_addr in this tree we need to make all
the writes to it go through appropriate helpers.

Even though the current code uses dev->addr_len the we can switch
to eth_hw_addr_set() instead of dev_addr_set(). The netdev is
always allocated by alloc_etherdev_mq() and there are at least two
places which assume Ethernet address:
- the line below calling eth_hw_addr_random()
- virtnet_set_mac_address() -> eth_commit_mac_addr_change()

Acked-by: Michael S. Tsirkin <[e-mail]>
Acked-by: Jason Wang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/virtio_net.c

···
 	dev->max_mtu = MAX_MTU;
 
 	/* Configuration may specify what MAC to use.  Otherwise random. */
-	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
+		u8 addr[ETH_ALEN];
+
 		virtio_cread_bytes(vdev,
 				   offsetof(struct virtio_net_config, mac),
-				   dev->dev_addr, dev->addr_len);
-	else
+				   addr, ETH_ALEN);
+		eth_hw_addr_set(dev, addr);
+	} else {
 		eth_hw_addr_random(dev);
+	}
 
 	/* Set up our device-specific information */
 	vi = netdev_priv(dev);