tty: add missing tty_port_tty_get() call to raw3215_wakeup

Fix compile error caused by "TTY: con3215, use tty from tty_port":

 CC      drivers/s390/char/con3215.o
drivers/s390/char/con3215.c: In function 'raw3215_wakeup':
drivers/s390/char/con3215.c:339:16: error: 'struct raw3215_info' has no member named 'tty'
make[1]: *** [drivers/s390/char/con3215.o] Error 1
make: *** [drivers/s390/char/] Error 2

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>