mtd: edit NAND-related comment

This comment was unclear regarding which NAND functions do and do not
support ECC on the spare area. This update should reflect the current
status of the NAND system but can be updated if changes are made in
the standard functions.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <dedekind1@gmail.com>

drivers/mtd/mtdchar.c

@@ -482,8 +482,9 @@ static int mtd_do_readoob(struct mtd_info *mtd, uint64_t start,
 	 * to signal the caller that a bitflip has occured and has
 	 * been corrected by the ECC algorithm.
 	 *
-	 * Note: most NAND ECC algorithms do not calculate ECC
-	 * for the OOB area.
+	 * Note: currently the standard NAND function, nand_read_oob_std,
+	 * does not calculate ECC for the OOB area, so do not rely on
+	 * this behavior unless you have replaced it with your own.
 	 */
 	if (ret == -EUCLEAN || ret == -EBADMSG)
 		return 0;