iget: stop FAT from using iget() and read_inode()

Stop the FAT filesystem from using iget() and read_inode().  Replace the call
to iget() with a call to ilookup().

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>