exfat: properly set s_time_gran

The s_time_gran superblock field indicates the on-disk nanosecond
granularity of timestamps, and for exfat that seems to be 10ms, so
set s_time_gran to 10000000ns. Without this, in-memory timestamps
change when they get re-read from disk.
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

fs/exfat/super.c

@@ -529,7 +529,7 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_magic = EXFAT_SUPER_MAGIC;
 	sb->s_op = &exfat_sops;
 
-	sb->s_time_gran = 1;
+	sb->s_time_gran = 10 * NSEC_PER_MSEC;
 	sb->s_time_min = EXFAT_MIN_TIMESTAMP_SECS;
 	sb->s_time_max = EXFAT_MAX_TIMESTAMP_SECS;