net: mscc: ocelot: be able to reuse a devlink_port after teardown

There are cases where we would like to continue probing the switch even
if one port has failed to probe. When that happens, we need to
unregister a devlink_port of type DEVLINK_PORT_FLAVOUR_PHYSICAL and
re-register it of type DEVLINK_PORT_FLAVOUR_UNUSED.

This is fine, except when calling devlink_port_attrs_set on a structure
on which devlink_port_register has been previously called, there is a
WARN_ON in devlink_port_attrs_set that devlink_port->devlink must be
NULL.

So don't assume that the memory behind dlp is clean when calling
ocelot_port_devlink_init, just zero-initialize it.
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mscc/ocelot_net.c

@@ -164,6 +164,7 @@ int ocelot_port_devlink_init(struct ocelot *ocelot, int port,
 	struct devlink *dl = ocelot->devlink;
 	struct devlink_port_attrs attrs = {};
 
+	memset(dlp, 0, sizeof(*dlp));
 	memcpy(attrs.switch_id.id, &ocelot->base_mac, id_len);
 	attrs.switch_id.id_len = id_len;
 	attrs.phys.port_number = port;