A 2M bytes SPI NOR flash(sst25vf016b) is soldered on the mx51_3ds
board.  So add the corresponding device for it.
Signed-off-by: NJason Wang <jason77.wang@gmail.com>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>