ARM: kirkwood: SBx81LIFKW: Enable network hardware

The SBx81LIFKW boards connect to the internal chassis management network
via a Marvell 88e6097 L2 switch. The chassis connections are direct
serdes on ports 8 and 9 with a RGMII interface on port 10 connected to
the CPU MAC.

For debugging purposes ports 0 and 1 are also taken out to headers on
the board. Because the debug interfaces are sometimes connected to with
straight ribbon cables we need to run them at 10Mbps.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>