net: dsa: mv88e6xxx: Add erratum 3.14 for 88E6390X and 88E6190X

Fixes XAUI/RXAUI lane alignment errors.
Issue causes dropped packets when trying to communicate over
fiber via SERDES lanes of port 9 and 10.
Errata document applies only to 88E6190X and 88E6390X devices.
Requires poking in undocumented registers.

Signed-off-by: Ante Knezic <ante.knezic@helmholz.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>