From: Vladimir Oltean <vladimir.oltean@xxxxxxx>
The dev_set_mtu() call from dsa_master_setup() has been effectively
superseded by the dsa_slave_change_mtu(slave_dev, ETH_DATA_LEN) that is
done from dsa_slave_create() for each user port. This function also
updates the master MTU according to the largest user port MTU from the
tree. Therefore, updating the master MTU through a separate code path
isn't needed.
Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>