staging: most: aim-network: setup mac address before ifup has finished

The networking AIM implements a non-standard behavior as it starts the
networking interface with an invalid MAC address and changes it by the time
a valid one is available.

This patch introduces a completion object to set the MAC address of the
networking interface before the .ndo_open callback (ifup) of the net_device
returns.

Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>