Networking: Divide net_intiialize() into net_setup() and net_initialize() to...

Networking: Divide net_intiialize() into net_setup() and net_initialize() to solve a chicken-and-egg problem.  net_setup() must be caleld before up_initialize() is called so that networking data structures are ready to register new network devices.

net_initialize() now does only timer related operations and is called AFTER up_initialize() where the timers are configured.  This is really.