ieee802154: hwsim: add replacement for fakelb

This patch adds a new virtual driver mac802154_hwsim which is based on
the fakelb driver.
The fakelb driver will get deprecated and hopefully removed someday.
The main reason for doing this step is to rename the driver to
mac802154_hwsim to have a similar naming scheme as mac80211_hwsim,
which is more popular in the 802.11 wireless word and the idea is the
same behind this driver.

The new features of this driver are to have knowledge about connected
edges, which can be changed during runtime. This offers a testing
environment for routing protocols e.g. RPL.
The default behaviour is still as fakelb: two radios connected to each
other. New added radios during runtime will not be connected to other
wpan_hwsim instances.

The netlink api is not namespace aware on purpose, only the registered
wpan_phy's can be moved to namespaces. The physical layer according to
wiresless "air" communication can be handled across namespaces.

Furthermore the edges can be weighted with the LQI value according IEEE
802.15.4 which offers additional handling to mark bad or good connection
indicators to other connected virtual phys.

Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>