mlxsw: core_thermal: Avoid creation of virtual hwmon objects by thermal module

The driver registers with both the hwmon and thermal subsystems.
Therefore, there is no need for the thermal subsystem to automatically
create hwmon entries upon registration of a thermal zone, as this
results in duplicate information.

Avoid creation of virtual hwmon objects by thermal subsystem by
registering a thermal zone with 'no_hwmon' set to 'true'.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>