USB: cdc-acm: fix break reporting

A recent change that started reporting break events forgot to push the
event to the line discipline, which meant that a detected break would
not be reported until further characters had been receive (the port
could even have been closed and reopened in between).

Fixes: 08dff274ed ("cdc-acm: fix BREAK rx code path adding necessary calls")
Cc: stable@vger.kernel.org
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210929090937.7410-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -340,6 +340,9 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
 			acm->iocount.overrun++;
 		spin_unlock_irqrestore(&acm->read_lock, flags);
 
+		if (newctrl & ACM_CTRL_BRK)
+			tty_flip_buffer_push(&acm->port);
+
 		if (difference)
 			wake_up_all(&acm->wioctl);