dpif-netdev: Allow different numbers of rx queues for different ports.

dpif-netdev: Allow different numbers of rx queues for different ports.

Currently, all of the PMD netdevs can only have the same number of
rx queues, which is specified in other_config:n-dpdk-rxqs.

Fix that by introducing of new option for PMD interfaces: 'n_rxq', which
specifies the maximum number of rx queues to be created for this
interface.

Example:
	ovs-vsctl set Interface dpdk0 options:n_rxq=8

Old 'other_config:n-dpdk-rxqs' deleted.

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Acked-by: Ben Pfaff <blp@ovn.org>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>