dpif-netdev: Introduce pmd-rxq-affinity.

dpif-netdev: Introduce pmd-rxq-affinity.

New 'other_config:pmd-rxq-affinity' field for Interface table to
perform manual pinning of RX queues to desired cores.

This functionality is required to achieve maximum performance because
all kinds of ports have different cost of rx/tx operations and
only user can know about expected workload on different ports.

Example:
	# ./bin/ovs-vsctl set interface dpdk0 options:n_rxq=4 \
	                  other_config:pmd-rxq-affinity="0:3,1:7,3:8"
	Queue #0 pinned to core 3;
	Queue #1 pinned to core 7;
	Queue #2 not pinned.
	Queue #3 pinned to core 8;

It's decided to automatically isolate cores that have rxq explicitly
assigned to them because it's useful to keep constant polling rate on
some performance critical ports while adding/deleting other ports
without explicit pinning of all ports.

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>