mtd: nand: s3c2410: fix bug in s3c2410_nand_correct_data()

If there is only one bit difference in the ECC, the function should
return 1.
The result of "diff0 & ~(1<<fls(diff0))" is equal to diff0, so the
function actually returns -1.
Signed-off-by: Zhaoxiu Zeng <zhaoxiu.zeng@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/nand/s3c2410.c

@@ -542,7 +542,8 @@ static int s3c2410_nand_correct_data(struct mtd_info *mtd, u_char *dat,
 	diff0 |= (diff1 << 8);
 	diff0 |= (diff2 << 16);
 
-	if ((diff0 & ~(1<<fls(diff0))) == 0)
+	/* equal to "(diff0 & ~(1 << __ffs(diff0)))" */
+	if ((diff0 & (diff0 - 1)) == 0)
 		return 1;
 
 	return -1;