mtd: mtdswap: fix printk format warning

The number is actually a sizeof(), so using %zu for it builds
cleanly on 32-bit or 64-bit.

drivers/mtd/mtdswap.c:1456: warning: format '%lu' expects type 'long unsigned int', but argument 4 has type 'unsigned int'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/mtdswap.c

@@ -1452,7 +1452,7 @@ static void mtdswap_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
 	oinfo = mtd->ecclayout;
 	if (!mtd->oobsize || !oinfo || oinfo->oobavail < MTDSWAP_OOBSIZE) {
 		printk(KERN_ERR "%s: Not enough free bytes in OOB, "
-			"%d available, %lu needed.\n",
+			"%d available, %zu needed.\n",
 			MTDSWAP_PREFIX, oinfo->oobavail, MTDSWAP_OOBSIZE);
 		return;
 	}