sfc: Use filter index rather than ID for rps_flow_id table

efx->type->filter_insert() returns an ID rather than the index that
 efx->type->filter_async_insert() used to, which causes it to exceed
 efx->type->max_rx_ip_filters on some EF10 configurations, leading to out-
 of-bounds array writes.
So, in efx_filter_rfs_work(), convert this back into an index (which is
 what the remove call in the expiry path expects, anyway).

Fixes: 3af0f34290f6 ("sfc: replace asynchronous filter operations")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/rx.c

@@ -839,6 +839,8 @@ static void efx_filter_rfs_work(struct work_struct *data)
 	int rc;
 
 	rc = efx->type->filter_insert(efx, &req->spec, true);
+	if (rc >= 0)
+		rc %= efx->type->max_rx_ip_filters;
 	if (efx->rps_hash_table) {
 		spin_lock_bh(&efx->rps_hash_lock);
 		rule = efx_rps_hash_find(efx, &req->spec);