mtd: rawnand: sunxi: sunxi_nand_ooblayout_free code clarification

The available length is really USER_DATA_LEN - 2 instead of just 2 (the
user data length minus the BBM length)
USER_DATA_LEN being 4, that doesn't change anything now, but if
USER_DATA_LEN changes, it will.

Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
Reviewed-by: Chen-Yu Tsai <wens@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: richard-bootlin

drivers/mtd/nand/raw/sunxi_nand.c

@@ -1755,12 +1755,12 @@ static int sunxi_nand_ooblayout_free(struct mtd_info *mtd, int section,
 
 	/*
 	 * The first 2 bytes are used for BB markers, hence we
-	 * only have 2 bytes available in the first user data
+	 * only have USER_DATA_SZ - 2 bytes available in the first user data
 	 * section.
 	 */
 	if (!section && ecc->engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST) {
 		oobregion->offset = 2;
-		oobregion->length = 2;
+		oobregion->length = USER_DATA_SZ - 2;
 
 		return 0;
 	}