svc: change ap_device_id messages to ap_id

The data payload of the ap_device_id message was exptended to include
the module id. The name was changed so adjust to match the greybus
spec and kernel greybus support.

Signed-off-by: Matt Porter <mporter@linaro.org>
gpio: Add soft gpio protocol handler

Add a software debug gpio protocol handler. This implements
a 4 line gpio device for all modules with cports claiming
gpio protocol support.

This will be extended with optional BeagleBone backend support
to access h/w gpios via the sysfs userspace interface.

Signed-off-by: Matt Porter <mporter@linaro.org>