tty: fix tty_port_block_til_ready waiting

Since commit 3e3b5c08 ("tty: use
prepare/finish_wait"), tty_port_block_til_ready() is using
prepare_to_wait()/finish_wait().  Those functions require that the
wait_queue_t be initialised with .func=autoremove_wake_function, via
DEFINE_WAIT().

But the conversion from DECLARE_WAITQUEUE() to DEFINE_WAIT() was not made,
so this code will oops in finish_wait().
Signed-off-by: NJiri Slaby <jirislaby@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/tty_port.c

@@ -193,7 +193,7 @@ int tty_port_block_til_ready(struct tty_port *port,
 {
 	int do_clocal = 0, retval;
 	unsigned long flags;
-	DECLARE_WAITQUEUE(wait, current);
+	DEFINE_WAIT(wait);
 	int cd;
 
 	/* block if port is in the process of being closed */