greybus: ap: process the UniPro link up message

greybus: ap: process the UniPro link up message

The link up message is the event that tells the AP what device ID
has been assigned to a particular interface on a module during
enumeration. The link up is sent *only* after the hotplug event
for a particular module has been sent to the AP.

The link up payload must carry the Module ID and Interface ID
to uniquely identify the struct gb_interface to which the
Device ID has been assigned.

After processing of the link up message, the interface's device_id
field will contain the assigned Device ID so that the AP has the
information necessary to issue network route commands.

Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>