usb: gadget: u_ether: fix regression in setting fixed MAC address

commit b337af3a upstream.

In systemd systems setting a fixed MAC address through
the "dev_addr" module argument fails systematically.
When checking the MAC address after the interface is created
it always has the same but different MAC address to the one
supplied as argument.

This is partially caused by systemd which by default will
set an internally generated permanent MAC address for interfaces
that are marked as having a randomly generated address.

Commit 890d5b40 ("usb: gadget: u_ether: fix race in
setting MAC address in setup phase") didn't take into account
the fact that the interface must be marked as having a set
MAC address when it's set as module argument.

Fixed by marking the interface with NET_ADDR_SET when
the "dev_addr" module argument is supplied.

Fixes: 890d5b40

 ("usb: gadget: u_ether: fix race in setting MAC address in setup phase")
Cc: stable@vger.kernel.org
Signed-off-by: Marian Postevca <posteuca@mutex.one>
Link: https://lore.kernel.org/r/20220603153459.32722-1-posteuca@mutex.one
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>