fs/autofs4/dev-ioctl.c: add __init to autofs_dev_ioctl_init

autofs_dev_ioctl_init is only called by __init init_autofs4_fs

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>