sfc: Fix conditions for MDIO self-test

The MDIO self-test should not be run on boards without an MDIO PHY,
such as SFN5122F-R3 and later revisions.  It should also not try to
address a specific MMD in an MDIO clause 22 PHY.  Check the
mode_support field to decide which mode to use, if any.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sfc/selftest.c

@@ -79,10 +79,14 @@ struct efx_loopback_state {
 static int efx_test_mdio(struct efx_nic *efx, struct efx_self_tests *tests)
 {
 	int rc = 0;
-	int devad = __ffs(efx->mdio.mmds);
+	int devad;
 	u16 physid1, physid2;
 
-	if (efx->phy_type == PHY_TYPE_NONE)
+	if (efx->mdio.mode_support & MDIO_SUPPORTS_C45)
+		devad = __ffs(efx->mdio.mmds);
+	else if (efx->mdio.mode_support & MDIO_SUPPORTS_C22)
+		devad = MDIO_DEVAD_NONE;
+	else
 		return 0;
 
 	mutex_lock(&efx->mac_lock);