[MTD] [NAND] platform NAND driver: add driver

This patch adds support for generic platform NAND driver.
Updated after tglx's review/discussion in IRC #mtd channel.

Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>