This patch changes network devices to run hotplug out of the
kobject/class_device infrastructure rather than calling it
from the network code.  The code gets simpler and there is
only one place for Greg to fix when he changes the API.

All hotplug now happens off the chain:
     rtnl_unlock -> netdev_run_todo -> netdev_sysfs_{un}register

The state flag deadbeef was converted to a state enumeration tp
handle necessary book keeping, and adds some defense against
drivers that have unexpected semantics.