USB: mos7840: fix broken TIOCMIWAIT

commit e670c6af12517d08a403487b1122eecf506021cf 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>