f2fs: fix wrong statistics of inline data

If we remove a file that has inline data after mount, our statistics turns to
inaccurate.

cat /sys/kernel/debug/f2fs/status
  - Inline_data Inode: 4294967295

Let's add stat_inc_inline_inode() to stat inline info of the file when lookup.

Change log from v1:
 o stat in f2fs_lookup() instead of in do_read_inode() for excluding wrong stat.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>