[PATCH] Remove unused tty_struct field

Unused: tty_struct.max_flip_cnt

$ git grep max_flip_cnt
include/linux/tty.h:    int max_flip_cnt;
$

Cc: Paul Fulghum <paulkf@microgate.com>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>