f2fs: fix to recover inode->i_flags of inode block during POR

Testcase to reproduce this bug:
1. mkfs.f2fs /dev/sdd
2. mount -t f2fs /dev/sdd /mnt/f2fs
3. touch /mnt/f2fs/file
4. sync
5. chattr +a /mnt/f2fs/file
6. xfs_io -a /mnt/f2fs/file -c "fsync"
7. godown /mnt/f2fs
8. umount /mnt/f2fs
9. mount -t f2fs /dev/sdd /mnt/f2fs
10. xfs_io /mnt/f2fs/file

There is no error when opening this file w/o O_APPEND, but actually,
we expect the correct result should be:

/mnt/f2fs/file: Operation not permitted

The root cause is, in recover_inode(), we recover inode->i_flags more
than F2FS_I(inode)->i_flags, so fix it.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>