mtd: rawnand: davinci: make platform_data private

There are no longer any users of the platform data for davinci rawnand
in board files. We can remove the public pdata headers and move the
structures that are still used into the driver compilation unit while
removing the rest.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240814122120.13975-1-brgl@bgdev.pl