mtd: kill the ecclayout->oobavail field

ecclayout->oobavail is just redundant with the mtd->oobavail field.
Moreover, it prevents static const definition of ecc layouts since the
NAND framework is calculating this value based on the ecclayout->oobfree
field.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/hisi504_nand.c

@@ -632,7 +632,6 @@ static void hisi_nfc_host_init(struct hinfc_host *host)
 }
 
 static struct nand_ecclayout nand_ecc_2K_16bits = {
-	.oobavail = 6,
 	.oobfree = { {2, 6} },
 };