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/tty/serial/nwpserial.c b/drivers/tty/serial/nwpserial.c
index 10d64a3..77287c5 100644
--- a/drivers/tty/serial/nwpserial.c
+++ b/drivers/tty/serial/nwpserial.c
@@ -129,7 +129,6 @@
 {
 	struct nwpserial_port *up = dev_id;
 	struct tty_port *port = &up->port.state->port;
-	struct tty_struct *tty = port->tty;
 	irqreturn_t ret;
 	unsigned int iir;
 	unsigned char ch;
@@ -150,7 +149,7 @@
 			tty_insert_flip_char(port, ch, TTY_NORMAL);
 	} while (dcr_read(up->dcr_host, UART_LSR) & UART_LSR_DR);
 
-	tty_flip_buffer_push(tty);
+	tty_flip_buffer_push(port);
 	ret = IRQ_HANDLED;
 
 	/* clear interrupt */