lib/netdev-dpdk: fix missing request.port_no in get_stats

The ovs-vswitchd cannot get the correct stats.

DPDK datapath will find the port_no from the request.port_name if the
port_no is UINT32_MAX. Otherwise use the port_no in request data.

In dpif_dpdk_port_get_stats(), ovs-vswitchd requests the stats with
port_name, but missing to set port_no UINT32_MAX causes unexpected
behavior. The ovs-vswitchd will get ENODEV error and fail to store
stats.

Set port_no to UINT32_MAX to work correctly.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Reviewed-by: Hayato Momma <h-momma@ce.jp.nec.com>