net/mlx5e: Enforce setting of a single FEC mode

Ethtool command allow setting of several FEC modes in a single set
command. The driver can only set a single FEC mode at a time. With this
patch driver will reply not-supported on setting several FEC modes.
Signed-off-by: Aya Levin <ayal@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c

@@ -1541,6 +1541,10 @@ static int mlx5e_set_fecparam(struct net_device *netdev,
 	int mode;
 	int err;
 
+	if (bitmap_weight((unsigned long *)&fecparam->fec,
+			  ETHTOOL_FEC_BASER_BIT + 1) > 1)
+		return -EOPNOTSUPP;
+
 	for (mode = 0; mode < ARRAY_SIZE(pplm_fec_2_ethtool); mode++) {
 		if (!(pplm_fec_2_ethtool[mode] & fecparam->fec))
 			continue;