USB: mos7840: fix broken TIOCMIWAIT

commit e670c6af upstream.

Make sure waiting processes are woken on modem-status changes.

Currently processes are only woken on termios changes regardless of
whether the modem status has changed.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/mos7840.c

@@ -453,6 +453,9 @@ static void mos7840_handle_new_msr(struct moschip_port *port, __u8 new_msr)
 			icount->rng++;
 			smp_wmb();
 		}
+
+		mos7840_port->delta_msr_cond = 1;
+		wake_up_interruptible(&mos7840_port->delta_msr_wait);
 	}
 }
 
@@ -2074,8 +2077,6 @@ static void mos7840_change_port_settings(struct tty_struct *tty,
 			mos7840_port->read_urb_busy = false;
 		}
 	}
-	wake_up(&mos7840_port->delta_msr_wait);
-	mos7840_port->delta_msr_cond = 1;
 	dbg("mos7840_change_port_settings mos7840_port->shadowLCR is End %x",
 	    mos7840_port->shadowLCR);
 }