nfp: flower-ct: compile match sections of flow_payload

Add in the code to compile match part of the payload that will be
sent to the firmware. This works similar to match.c does it, but
since three flows needs to be merged it iterates through all three
rules in a loop and combine the match fields to get the most strict
match as result.

Signed-off-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>