nfp: bring back support for offloading shared blocks

Now that we have offload replay infrastructure added by
commit 32636742 ("net: sched: call reoffload op on block callback reg")
and flows are guaranteed to be removed correctly, we can revert
commit 951a8ee6

 ("nfp: reject binding to shared blocks").

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>