mtd: spi-nor: s25fl008k and s25fl016k supports dual/quad mode

s25fl016k can be found on Embedded Artists' LPC4357 Developer's Kit
where is used in quad mode by the LPC4357 SPIFI controller.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>