sfc: Check firmware supports Ethernet PTP filter

Not all firmware variants support RSS filters. Do not fail all PTP
functionality when raw ethernet PTP filters fail to insert.

Fixes: e4616f64 ("sfc: support PTP over Ethernet")
Signed-off-by: Alex Austin <alex.austin@amd.com>
Acked-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@amd.com>
Link: https://lore.kernel.org/r/20230824164657.42379-1-alex.austin@amd.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/sfc/ptp.c

@@ -1485,7 +1485,9 @@ static int efx_ptp_insert_multicast_filters(struct efx_nic *efx)
 			goto fail;
 
 		rc = efx_ptp_insert_eth_multicast_filter(efx);
-		if (rc < 0)
+
+		/* Not all firmware variants support this filter */
+		if (rc < 0 && rc != -EPROTONOSUPPORT)
 			goto fail;
 	}