Commits b02f5ad6 ("istallion: use
tty_port") and a352def2 ("tty: Ldisc
revamp") broke the istallion driver.

Fix the compile error and silence a warning.
Signed-off-by: NWang Chen <wangchen@cn.fujitsu.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>