mtd: rawnand: marvell: fix spelling mistake in kernel doc

Correct the spelling mistake 'Regiters' -> 'Registers'.

Fixes: 961ba15c ("mtd: rawnand: marvell: Fix clock resource by adding a register clock")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>