mlxsw: Treat local port 64 as valid

MLXSW_PORT_MAX_PORTS represents the maximum number of local ports, which
is 65 for both ASICs (SwitchX-2 and Spectrum) supported by this driver.

Fixes: 93c1edb2 ("mlxsw: Introduce Mellanox switch driver core")
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>