mtd: nand: Add mvebu (PXA / AXP / A38x) NAND device driver

mtd: nand: Add mvebu (PXA / AXP / A38x) NAND device driver

Cloned from the Linux driver v4.2.0-rc2. Plus some patches from
Antoine Tenart enabling controller initialization and ONFI timing
support:

http://lists.infradead.org/pipermail/linux-mtd/2015-July/060197.html

Please note that this driver needs the Linux NAND subsystem sync to v4.1
from Scott to be applied:

https://www.mail-archive.com/[email protected]/msg175762.html

Otherwise it will not compile.

Tested on the Marvell Armada XP DB-MV784MP-GP eval board.

Signed-off-by: Stefan Roese <[email protected]>
Cc: Antoine Tenart <[email protected]>
Cc: Ezeguil Garcia <[email protected]>
Cc: Luka Perkov <[email protected]>
Cc: Scott Wood <[email protected]>