MIPS/mtd: Handle READY GPIO in generic NAND platform data

MIPS/mtd: Handle READY GPIO in generic NAND platform data

The callbacks into the MIPS RB532 platform to read the GPIO pin
indicating that the NAND chip is ready are oldschool and does
not assign GPIOs as properties to the NAND device.

Add a capability to the generic platform NAND chip driver to use
a GPIO line to detect if a NAND chip is ready and override the
platform-local drv_ready() callback with this check if the GPIO
is present.

This makes it possible to drop the legacy include header
<linux/gpio.h> from the RB532 devices.

Signed-off-by: Linus Walleij <linusw@kernel.org>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>