cfg802154: convert deprecated iface add and del

This patch removes the wpan_phy callbacks for add and del an interface
on a phy. Instead we introduce deprecated cfg802154 callbacks for this.
Furthermore we introduce a new netlink interface nl802154 which use
different callbacks. The deprecated function is to have a backwards
compatibility with the current netlink interface.

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