This adds simple direction calculation when combining effects. It's useful
to decide motor direction for rumble (vibrator).
Signed-off-by: NJari Vanhala <ext-jari.vanhala@nokia.com>
Acked-by: NAnssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>