udoo: Add ethernet support (FEC + Micrel KSZ9031).

Add Ethernet and networking support on uDoo board (FEC +phy Micrel KSZ9031).
Ethernet speed is currently limited to 10/100Mbps.

Signed-off-by: Giuseppe Pagano <giuseppe.pagano@seco.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
CC: Stefano Babic <sbabic@denx.de>
CC: Fabio Estevam <fabio.estevam@freescale.com>