dpif-netdev: Rework rxq scheduling code.

This reworks the current rxq scheduling code to break it into more
generic and reusable pieces.

The behaviour does not change from a user perspective, except the logs
are updated to be more consistent.

From an implementation view, there are some changes with mind to
extending functionality.

The high level reusable functions added in this patch are:
- Generate a list of current numas and pmds
- Perform rxq scheduling assignments into that list
- Effect the rxq scheduling assignments so they are used

Signed-off-by: Kevin Traynor <[email protected]>
Acked-by: Sunil Pai G <[email protected]>
Acked-by: David Marchand <[email protected]>
Signed-off-by: Ian Stokes <[email protected]>