mtd: rawnand: Remove unused of_gpio.h inclusion

The of_gpio.h is not and shouldn't be used in the drivers. Remove it.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>