mtd: nand: ecc-hamming: Use the public nsteps field

The software Hamming ECC engine stores the nsteps variable in its own
private structure while it is also exported as a public ECC field.

Let's get rid of the redundant private one and let's use the
nand_ecc_context structure when possible.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Adam Ford <aford173@gmail.com> #logicpd Torpedo
Link: https://lore.kernel.org/linux-mtd/20210127203020.9574-10-miquel.raynal@bootlin.com

mtd: nand: ecc-hamming: Create the software Hamming engine

Let's continue introducing the generic ECC engine abstraction in the
NAND subsystem by instantiating a second ECC engine: software
Hamming.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-20-miquel.raynal@bootlin.com

mtd: nand: ecc-hamming: Let the software Hamming ECC engine be unselected

There is no reason to always embed the software Hamming ECC engine
implementation. By default it is (with raw NAND), but we can let the
user decide.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-19-miquel.raynal@bootlin.com

mtd: nand: ecc-hamming: Stop using raw NAND structures

This code is meant to be reused by the SPI-NAND core. Now that the
driver has been cleaned and reorganized, use a generic ECC engine
object to store the driver's data instead of accessing members of the
nand_chip structure. This means adding proper init/cleanup helpers.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-17-miquel.raynal@bootlin.com

mtd: nand: ecc-hamming: Rename the exported functions

Prefix by ecc_sw_hamming_ the functions which should be internal only
but are exported for "raw" operations.

Prefix by nand_ecc_sw_hamming_ the other functions which will be used
in the context of the declaration of an Hamming proper ECC engine
object.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-16-miquel.raynal@bootlin.com

mtd: nand: ecc-hamming: Clarify the driver descriptions

The include file pretends being the header for "ECC algorithm", while
it is just the header for the Hamming implementation. Make this clear
by rewording the sentence.

Do the same with the module description.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-13-miquel.raynal@bootlin.com

mtd: nand: ecc-hamming: Move Hamming code to the generic NAND layer

Hamming ECC code might be later re-used by the SPI NAND layer.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-12-miquel.raynal@bootlin.com