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/ehv_bytechan.c b/drivers/tty/ehv_bytechan.c
index 5164f9a..ed92622 100644
--- a/drivers/tty/ehv_bytechan.c
+++ b/drivers/tty/ehv_bytechan.c
@@ -371,16 +371,11 @@
 static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
 {
 	struct ehv_bc_data *bc = data;
-	struct tty_struct *ttys = tty_port_tty_get(&bc->port);
 	unsigned int rx_count, tx_count, len;
 	int count;
 	char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
 	int ret;
 
-	/* ttys could be NULL during a hangup */
-	if (!ttys)
-		return IRQ_HANDLED;
-
 	/* Find out how much data needs to be read, and then ask the TTY layer
 	 * if it can handle that much.  We want to ensure that every byte we
 	 * read from the byte channel will be accepted by the TTY layer.
@@ -422,9 +417,7 @@
 	}
 
 	/* Tell the tty layer that we're done. */
-	tty_flip_buffer_push(ttys);
-
-	tty_kref_put(ttys);
+	tty_flip_buffer_push(&bc->port);
 
 	return IRQ_HANDLED;
 }