atl1c: fix Mikrotik 10/25G NIC detection

Since Mikrotik 10/25G NIC MDIO op emulation is not 100% reliable,
on rare occasions it can happen that some physical functions of
the NIC do not get initialized due to timeouted early MDIO op.

This changes the atl1c probe on Mikrotik 10/25G NIC not to
depend on MDIO op emulation.

Signed-off-by: Gatis Peisenieks <gatis@mikrotik.com>
Signed-off-by: David S. Miller <davem@davemloft.net>