vlan network devices have devices nesting below it, and are a special
"super class" of normal network devices; split their locks off into a
separate class since they always nest.

[deweerdt@free.fr: fix possible null-pointer deref]
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NFrederik Deweerdt <frederik.deweerdt@gmail.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>