net: sfp: add quirk for another multigig RollBall transceiver

Add quirk for another RollBall copper transceiver: Turris RTSFP-2.5G,
containing 2.5g capable RTL8221B PHY.

Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Eric Woudstra <ericwouds@gmail.com>

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>