fakelb: introduce fakelb ifup phys list

This patch introduce a fakelb ifup phys list, which stores all
registered phys which are in an operated mode. This will reduce the
iterations of non-operated phys while transmit frames. There exists two
locks now, one rwlock for the operated interfaces and the spinlock for
protecting the list for all registered virtual phys.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>