atmel/nand: add DT support

Use a local copy of board informatin and fill with DT data.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>