net: Statically initialize init_net.dev_base_head

commit 734b65417b24d6eea3e3d7457e1f11493890ee1d upstream.

This change eliminates an initialization-order hazard most
recently seen when netprio_cgroup is built into the kernel.

With thanks to Eric Dumazet for catching a bug.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>