TTY: switch tty_insert_flip_char

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.

tty_insert_flip_char is the next one to proceed. This one is used all
over the code, so the patch is huge.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/fwserial/fwserial.c b/drivers/staging/fwserial/fwserial.c
index 85dbdc1..a2a0c43 100644
--- a/drivers/staging/fwserial/fwserial.c
+++ b/drivers/staging/fwserial/fwserial.c
@@ -617,7 +617,7 @@
 
 	lsr &= port->status_mask;
 	if (lsr & ~port->ignore_mask & UART_LSR_OE) {
-		if (!tty_insert_flip_char(tty, 0, TTY_OVERRUN)) {
+		if (!tty_insert_flip_char(&port->port, 0, TTY_OVERRUN)) {
 			err = -EIO;
 			goto out;
 		}