mtd: spinand: Fix kernel doc
The @data buffer is 5 bytes, not 4, it has been extended for the need of
devices with an extra ID bytes.
Fixes: 34a956739d29 ("mtd: spinand: Add support for 5-byte IDs")
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>