mtd: nand: Fix a kdoc comment

The max_bad_eraseblocks_per_lun member of nand_device obviously
describes a number of *maximum* number of bad eraseblocks per LUN.

Fix this obvious typo.

Fixes: 377e517b ("mtd: nand: Add max_bad_eraseblocks_per_lun info to memorg")
Cc: <stable+noautosel@kernel.org> # fix kdoc comment
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>