GetMaster() currently requires an attached slave device as parameter,
resuling in many calls being IsFloating(dev) ? dev : GetMaster(...);
Add two new parameters so GetMaster can be called unconditionally to get the
right device.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>