net: dsa: mt7530: do not pass port variable to mt7531_rgmii_setup()

The mt7531_rgmii_setup() function does not use the port variable, do not
pass the variable to it.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: David S. Miller <davem@davemloft.net>