USB: ch341: fix TIOCMIWAIT and disconnect

Use tty-port modem-status-change wait queue on which processes are woken
up at hangup and disconnect.

Currently a process waiting on modem-status changes will not be woken on
device disconnect as wake up was only done in dtr_rts which isn't
guaranteed to be called (e.g. if HUPCL is not set).

Also remove the redundant wake-up call from dtr_rts.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/ch341.c

@@ -296,7 +296,6 @@ static void ch341_dtr_rts(struct usb_serial_port *port, int on)
 		priv->line_control &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
 	spin_unlock_irqrestore(&priv->lock, flags);
 	ch341_set_handshake(port->serial->dev, priv->line_control);
-	wake_up_interruptible(&port->delta_msr_wait);
 }
 
 static void ch341_close(struct usb_serial_port *port)
@@ -489,7 +488,7 @@ static void ch341_read_int_callback(struct urb *urb)
 			tty_kref_put(tty);
 		}
 
-		wake_up_interruptible(&port->delta_msr_wait);
+		wake_up_interruptible(&port->port.delta_msr_wait);
 	}
 
 exit:
@@ -516,7 +515,7 @@ static int ch341_tiocmiwait(struct tty_struct *tty, unsigned long arg)
 	spin_unlock_irqrestore(&priv->lock, flags);
 
 	while (!multi_change) {
-		interruptible_sleep_on(&port->delta_msr_wait);
+		interruptible_sleep_on(&port->port.delta_msr_wait);
 		/* see if a signal did it */
 		if (signal_pending(current))
 			return -ERESTARTSYS;