fix AT91_DDRSDRC_MODE it's 3bit

add missing AT91_DDRSDRC_NR_14, AT91_DDRSDRC_DBW (16 and 32 bits support)
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>