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