TTY: isdn, use open/close_wait from tty_port

Hmm, the isdn ones were initialized twice.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Karsten Keil <isdn@linux-pingi.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/isdn.h

@@ -483,7 +483,6 @@ typedef struct modem_info {
 #endif
   struct tty_struct 	*tty;            /* Pointer to corresponding tty   */
   atemu                 emu;             /* AT-emulator data               */
-  wait_queue_head_t	open_wait, close_wait;
   spinlock_t	        readlock;
 } modem_info;