ARM: Kirkwood: convert rd88f6281-setup.c to DT.

Perform a mechanical translation of rd88f6281-setup.c into DT.  Since
the hardware differs between the A0 and A1 stepping, two dts files are
used, and a .dtsi file for the common parts. The A0 part does not have
a "wan" port on the switch and uses PHY address 10 to address the
switch. The A1 part does have the "wan" port and uses address 0.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>