mtd: rawnand: arasan: stop using 0 as NULL pointer

Fix the following sparse warnings:

drivers/mtd/nand/raw/arasan-nand-controller.c:918:70: warning: Using plain integer as NULL pointer
drivers/mtd/nand/raw/arasan-nand-controller.c:918:73: warning: Using plain integer as NULL pointer
Signed-off-by: GONG, Ruiqi <gongruiqi1@huawei.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220725112108.686347-1-gongruiqi1@huawei.com

drivers/mtd/nand/raw/arasan-nand-controller.c

@@ -915,7 +915,7 @@ static int anfc_check_op(struct nand_chip *chip,
 			if (instr->ctx.data.len > ANFC_MAX_CHUNK_SIZE)
 				return -ENOTSUPP;
 
-			if (anfc_pkt_len_config(instr->ctx.data.len, 0, 0))
+			if (anfc_pkt_len_config(instr->ctx.data.len, NULL, NULL))
 				return -ENOTSUPP;
 
 			break;