bonding: 3ad: Print an error for unknown speeds

The bond driver needs to be patched to support new ethtool speeds.
Currently it emits a single warning [1] when it encounters an unknown
speed. As evident by the two previous patches, this is not explicit
enough. Instead, promote it to an error.

[1]
bond10: (slave swp1): unknown ethtool speed (200000) for port 1 (set it to 0)

v2:
* Use pr_err_once() instead of WARN_ONCE()
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_3ad.c

@@ -327,7 +327,7 @@ static u16 __get_link_speed(struct port *port)
 		default:
 			/* unknown speed value from ethtool. shouldn't happen */
 			if (slave->speed != SPEED_UNKNOWN)
-				pr_warn_once("%s: (slave %s): unknown ethtool speed (%d) for port %d (set it to 0)\n",
+				pr_err_once("%s: (slave %s): unknown ethtool speed (%d) for port %d (set it to 0)\n",
 					    slave->bond->dev->name,
 					    slave->dev->name, slave->speed,
 					    port->actor_port_number);