mtd: nand: don't walk past end of oobfree[]

Resolve issue noted by Sneha:  when computing oobavail from
the list of free areas in the OOB, don't assume there will
always be an unused slot at the end.  With ECC_HW_SYNDROME
and 4KiB page chips, it's fairly likely there *won't* be one.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Cc: "Narnakaje, Snehaprabha" <nsnehaprabha@ti.com>"
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/nand_base.c

@@ -2756,7 +2756,8 @@ int nand_scan_tail(struct mtd_info *mtd)
 	 * the out of band area
 	 */
 	chip->ecc.layout->oobavail = 0;
-	for (i = 0; chip->ecc.layout->oobfree[i].length; i++)
+	for (i = 0; chip->ecc.layout->oobfree[i].length
+			&& i < ARRAY_SIZE(chip->ecc.layout->oobfree); i++)
 		chip->ecc.layout->oobavail +=
 			chip->ecc.layout->oobfree[i].length;
 	mtd->oobavail = chip->ecc.layout->oobavail;