usb: gadget: u_ether: use eth_hw_addr_set()

usb: gadget: u_ether: 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 got through appropriate helpers.

Reviewed-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20211019172124.1413620-1-kuba@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>