net: sched: extract bstats update code into function

Extract common code that increments cpu_bstats counter into standalone act
API function. Change hardware offloaded actions that use percpu counter
allocation to use the new function instead of incrementing cpu_bstats
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>