dpif-netdev: Add rxq processing cycle counters.

dpif-netdev: Add rxq processing cycle counters.

Add counters to dp_netdev_rxq which will later be used for storing the
processing cycles of an rxq. Processing cycles will be stored in reference
to a defined time interval. We will store the cycles of the current in progress
interval, a number of completed intervals and the sum of the completed
intervals.

cycles_count_intermediate was used to count cycles for a pmd. With some small
additions we can also use it to count the cycles used for processing an rxq.

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Signed-off-by: Darrell Ball <dlu998@gmail.com>