mtd: Fix typo in mtd_ooblayout_set_databytes() description

Fix a probable copy/paste error: the function works like
mtd_ooblayout_set_bytes(), not *_get_bytes().

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200526195633.11543-2-miquel.raynal@bootlin.com

drivers/mtd/mtdcore.c

@@ -1800,7 +1800,7 @@ EXPORT_SYMBOL_GPL(mtd_ooblayout_get_databytes);
  * @start: first ECC byte to set
  * @nbytes: number of ECC bytes to set
  *
- * Works like mtd_ooblayout_get_bytes(), except it acts on free bytes.
+ * Works like mtd_ooblayout_set_bytes(), except it acts on free bytes.
  *
  * Returns zero on success, a negative error code otherwise.
  */