board: cssi: Add new board MCR3000_2G

This adds a new board from CS GROUP. The board is called
MCR3000_2G, and has a CPU board called CMPC885.

That CPU board is shared with another equipment that will
be added in a later patch.

That board stores Ethernet MAC addresses in an EEPROM which
is accessed using SPI bus.

This patch was originally written by Charles Frey who's
email address is not valid anymore as he left the company.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: FRANJOU Stephane <stephane.franjou@csgroup.eu>