core: remove unneded headers for net cgroup controllers.

commit 3ed80a62 (cgroup: drop module support) made including
module.h redundant in the net cgroup controllers,
netclassid_cgroup.c and netprio_cgroup.c. This patch
removes them.

Signed-off-by: Rami Rosen <rami.rosen@intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>