net: l2: ieee802154: AF_PACKET support for IEEE 802.15.4

This change makes the packet socket and ieee802154 l2 drivers aware of
AF_PACKET sockets, see https://github.com/linux-wpan/wpan-tools/tree/master/examples


for examples which inspired this change.

Signed-off-by: Florian Grandel <jerico.dev@gmail.com>