mlxsw: spectrum: Introduce port splitting

Allow a user to split or unsplit a port using the newly introduced
devlink ops.

Once split, the original netdev is destroyed and 2 or 4 others are
created, according to user configuration. The new ports are like any
other port, with the sole difference of supporting a lower maximum
speed. When unsplit, the reverse process takes place.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/mellanox/mlxsw/port.h b/drivers/net/ethernet/mellanox/mlxsw/port.h
index ae65b99..f33b997 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/port.h
+++ b/drivers/net/ethernet/mellanox/mlxsw/port.h
@@ -59,6 +59,8 @@
 
 #define MLXSW_PORT_DONT_CARE		(MLXSW_PORT_MAX_PORTS)
 
+#define MLXSW_PORT_MODULE_MAX_WIDTH	4
+
 enum mlxsw_port_admin_status {
 	MLXSW_PORT_ADMIN_STATUS_UP = 1,
 	MLXSW_PORT_ADMIN_STATUS_DOWN = 2,