net: openvswitch: optimize flow mask cache hash collision

Port the codes to linux upstream and with little changes.

Pravin B Shelar, says:
| In case hash collision on mask cache, OVS does extra flow
| lookup. Following patch avoid it.

Link: https://github.com/openvswitch/ovs/commit/0e6efbe2712da03522532dc5e84806a96f6a0dd1


Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Tested-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>