dpif-netdev: Change rxq_scheduling to use rxq processing cycles.

dpif-netdev: Change rxq_scheduling to use rxq processing cycles.

Previously rxqs were assigned to pmds by round robin in
port/queue order.

Now that we have the processing cycles used for existing rxqs,
use that information to try and produced a better balanced
distribution of rxqs across pmds. i.e. given multiple pmds, the
rxqs which have consumed the largest amount of processing cycles
will be placed on different pmds.

The rxqs are sorted by their processing cycles and assigned (in
sorted order) round robin across pmds.

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