MFC r347204:
Adds sys/class/net devices to linsysfs.
Only two interfaces are created eth0 and lo and they expose
the following properties:
address, addr_len, flags, ifindex, mty, tx_queue_len and type.
Initial patch developed by Carlos Neira in 2017 and finished by me.
MFC r347218:
Remove wrong copyright line. Discussed with Carlos Neira.