flow_dissector: Abstract out hash computation

Move the hash computation located in __skb_get_hash to be a separate
function which takes flow_keys as input. This will allow flow hash
computation in other contexts where we only have addresses and ports.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/net/flow_keys.h
Simple merge

diff --cc net/core/flow_dissector.c
Simple merge