nfp: flower-ct: add tc merge functionality

Add merging of pre/post_ct flow rules into the tc_merge table.
Pre_ct flows needs to be merge with post_ct flows and vice versa.

This needs to be done for all flows in the same zone table, as well
as with the wc_zone_table, which is for flows masking out ct_zone
info.

Cleanup is happening when all the tables are cleared up and prints
a warning traceback as this is not expected in the final version.
At this point we are not actually returning success for the offload,
so we do not get any delete requests for flows, so we can't delete
them that way yet. This means that cleanup happens in what would
usually be an exception path.

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>