Russell King correctly pointed out that the MAC_2500FD capability is
already added for port 5 (if not in RGMII mode) and port 6 (which only
supports SGMII) by mt7531_mac_port_get_caps. Remove the reduntant
setting of this capability flag which was added by a previous commit.

Fixes: e19de30d ("net: dsa: mt7530: add support for in-band link status")
Reported-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/Y5qY7x6la5TxZxzX@makrotopia.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>