net: virtio: use eth_hw_addr_set()

Commit 406f42fa ("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 <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20211027152012.3393077-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>