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

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

efs_fill_super() returns any error incurred when getting the root inode
instead of EACCES.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: David Howells <dhowells@redhat.com>
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>