TTY: switch tty_flip_buffer_push

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.

Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.

IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.

Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index 293b460..a547c91 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -275,7 +275,6 @@
 	int err;
 	int endpoint;
 	struct usb_serial_port *port;
-	struct tty_struct *tty;
 	struct device *dev;
 	unsigned char *data = urb->transfer_buffer;
 	int status = urb->status;
@@ -288,16 +287,12 @@
 		dev_dbg(dev, "%s: nonzero status: %d on endpoint %02x.\n",
 			__func__, status, endpoint);
 	} else {
-		tty = tty_port_tty_get(&port->port);
-		if (tty) {
-			if (urb->actual_length) {
-				tty_insert_flip_string(&port->port, data,
-						urb->actual_length);
-				tty_flip_buffer_push(tty);
-			} else
-				dev_dbg(dev, "%s: empty read urb received\n", __func__);
-			tty_kref_put(tty);
-		}
+		if (urb->actual_length) {
+			tty_insert_flip_string(&port->port, data,
+					urb->actual_length);
+			tty_flip_buffer_push(&port->port);
+		} else
+			dev_dbg(dev, "%s: empty read urb received\n", __func__);
 
 		/* Resubmit urb so we continue receiving */
 		err = usb_submit_urb(urb, GFP_ATOMIC);