When we initialize the driver/device, we really don't know how many
controllers are connected.  So send a "query presence" command to the
base-station. (Command discovered by Zachary Lund)

Presence packet taken from:

https://github.com/computerquip/xpad5Signed-off-by: Pavel Rojtberg <rojtberg@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>