Add support for Power Management to reduce CPU usage

[marcusschiesser]

Not a big issue for me, just adding it for completion.

To my knowledge, nff-go programs are currently using 100% of each assigned CPU core.

DPDK includes an example that sleeps on low load, see: https://doc.dpdk.org/guides-16.04/sample_app_ug/l3_forward_power_man.html

Feature request is to include this power management as an option to nff-go