[ROSE] lockdep: fix false positive

ROSE network devices are virtual network devices encapsulating ROSE
frames into AX.25 which will be sent through an AX.25 device, so form a
special "super class" of normal net devices; split their locks off into
a separate class since they always nest.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>