Add Atmel at25df321 spi-nor flash to the list of spi_nor_ids.

Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Jagan Teki <jteki@openedev.com>
Acked-by: Wenyou Yang <wenyou.yang@atmel.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>