net: sched: push chain dump to a separate function

Since there will be multiple chains to dump, push chain dumping code to
a separate function.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>