ARM: dts: kirkwood: set Guruplug ethernet PHY compatible

Ethernet PHY compatible shall be "ethernet-phy-ieee802.3-c22" and
"ethernet-phy-idAAAA.BBBB" if PHY OUI id is known. We know it for
the PHY found on Guruplug, so set it accordingly.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1398862602-29595-15-git-send-email-sebastian.hesselbarth@gmail.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>