nfp: flower: prevent offload if rhashtable insert fails

nfp: flower: prevent offload if rhashtable insert fails

For flow offload adds, if the rhash insert code fails, the flow will still
have been offloaded but the reference to it in the driver freed.

Re-order the offload setup calls to ensure that a flow will only be written
to FW if a kernel reference is held and stored in the rhashtable. Remove
this hashtable entry if the offload fails.

Fixes: c01d0efa5136 ("nfp: flower: use rhashtable for flow caching")
Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>