Add support for Eukrea's CPUIMX25 ...

This boards integrates 64mB of DDR, a 256MB NAND flash, a RMII Ethernet PHY
and a i.MX257 CPU.

Signed-off-by: Eric Bénard <eric@eukrea.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>