f2fs: enable quota at remount from r to w

We have to enable quota only when remounting from read to write. Otherwise,
we'll get remount failure. (e.g., write to write case)
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -1265,7 +1265,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		err = dquot_suspend(sb, -1);
 		if (err < 0)
 			goto restore_opts;
-	} else {
+	} else if (f2fs_readonly(sb) && !(*flags & MS_RDONLY)) {
 		/* dquot_resume needs RW */
 		sb->s_flags &= ~SB_RDONLY;
 		if (sb_any_quota_suspended(sb)) {