net: sched: extract qstats update code into functions

Extract common code that increments cpu_qstats counters into standalone act
API functions. Change hardware offloaded actions that use percpu counter
allocation to use the new functions instead of accessing cpu_qstats
directly.

This commit doesn't change functionality.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>