atl1c: show correct link speed on Mikrotik 10/25G NIC

The new Mikrotik 10/25G NIC maintains compatibility with existing atl1c
driver. However it does have new features.

This defines some new register offsets, code for identifying the new type
of NIC and correct speed detection for the NIC.

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