sf: probe: Add missing Atmel at25df321 flash

As the spi flash transfer to multiple parts, it is forgot to add
Atmel AT25DF321 spi flash support, which broken several Atmel EK
boards which this chip. So, add it

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
1 file changed