mtd: spinand: Use the external ECC engine logic

Now that all the logic is available in the NAND core, let's use it
from the SPI-NAND core. Right now there is no functional change as the
default ECC engine for SPI-NANDs is set to 'on-die', but user can now
use software correction if they want to by just setting the right
properties in the DT.

Also note that the OOB layout handling is removed from the SPI-NAND
core as each ECC engine is supposed to handle it by it's own; users
should not be aware of that.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20201001102014.20100-4-miquel.raynal@bootlin.com

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mtd: nand: Add core infrastructure to support SPI NANDs

Add a SPI NAND framework based on the generic NAND framework and the
spi-mem infrastructure.

In its current state, this framework supports the following features:

- single/dual/quad IO modes
- on-die ECC

Signed-off-by: Peter Pan <peterpandong@micron.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>