Add support for the ZII SCU 4 board, which has lots of switches and
SFF ports.

Based on the work from Andrew Lunn.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Chris Healy <cphealy@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>