nfp: bpf: reject TC offload if XDP loaded

Recent TC changes dropped the check protecting us from trying
to offload a TC program if XDP programs are already loaded.

Fixes: 90d97315 ("nfp: bpf: Convert ndo_setup_tc offloads to block callbacks")
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NSimon Horman <simon.horman@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/bpf/main.c

@@ -130,6 +130,9 @@ static int nfp_bpf_setup_tc_block_cb(enum tc_setup_type type,
 		    cls_bpf->common.protocol != htons(ETH_P_ALL) ||
 		    cls_bpf->common.chain_index)
 			return -EOPNOTSUPP;
+		if (nn->dp.bpf_offload_xdp)
+			return -EBUSY;
+
 		return nfp_net_bpf_offload(nn, cls_bpf);
 	default:
 		return -EOPNOTSUPP;