openvswitch: Use correct reply values in datapath and vport ops

This patch fixes the bug that all datapath and vport ops are returning
wrong values (OVS_FLOW_CMD_NEW or OVS_DP_CMD_NEW) in their replies.

Signed-off-by: Yifeng Sun <pkusunyifeng@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>