Remove the unused inode field of the autofs dentry info structure.

Link: https://lkml.kernel.org/r/165724460393.30914.6511330213821246793.stgit@donald.themaw.netSigned-off-by: Ian Kent <raven@themaw.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>