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

Stop the UFS filesystem from using iget() and read_inode().  Replace
ufs_read_inode() with ufs_iget(), and call that instead of iget().  ufs_iget()
then uses iget_locked() directly and returns a proper error code instead of an
inode in the event of an error.

ufs_fill_super() returns any error incurred when getting the root inode
instead of EINVAL.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
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>