nfp: flower: support ct merging when mangle action exists

nfp: flower: support ct merging when mangle action exists

Current implementation of ct merging doesn't support the case
that the fields mangling in pre_ct rules are matched in post_ct
rules.

This change is to support merging when mangling mac address,
ip address, tos, ttl and l4 port. VLAN and MPLS mangling is
not involved yet.

Signed-off-by: Yinjun Zhang <yinjun.zhang@corigine.com>
Signed-off-by: Louis Peens <louis.peens@corigine.com>
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20220518075055.130649-1-simon.horman@corigine.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>