openvswitch: Pack struct sw_flow_key.

struct sw_flow_key has two 16-bit holes. Move the most matched
conntrack match fields there.  In some typical cases this reduces the
size of the key that needs to be hashed into half and into one cache
line.

Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Joe Stringer <joe@ovn.org>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>