nfp: flower-ct: remove callback delete deadlock

The current location of the callback delete can lead to a race
condition where deleting the callback requires a write_lock on
the nf_table, but at the same time another thread from netfilter
could have taken a read lock on the table before trying to offload.
Since the driver is taking a rtnl_lock this can lead into a deadlock
situation, where the netfilter offload will wait for the cls_flower
rtnl_lock to be released, but this cannot happen since this is
waiting for the nf_table read_lock to be released before it can
delete the callback.

Solve this by completely removing the nf_flow_table_offload_del_cb
call, as this will now be cleaned up by act_ct itself when cleaning
up the specific nf_table.

Fixes: 62268e78 ("nfp: flower-ct: add nft callback stubs")
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>