In SwitchX-2 we configure the port speed to negotiate with 40G link only.
Add support for all other supported speeds.

Fixes: 31557f0f ("mlxsw: Introduce Mellanox SwitchX-2 ASIC support")
Signed-off-by: NElad Raz <eladr@mellanox.com>
Reviewed-by: NJiri Pirko <jiri@mellanox.com>
Reviewed-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>