net: dsa: sja1105: make sure the retagging port is enabled for SJA1110

The SJA1110 has an extra configuration in the General Parameters Table
through which the user can select the buffer reservation config.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>