net: dsa: mv88e6xxx: 6161 uses global 2 for PHY access

Access to the internal PHYs of the 6161 and 6123 go through global 2
SMI registers. Fix the ops structure.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>