mlxsw: core_env: Read module temperature thresholds using MTMP register

Currently, module temperature thresholds are obtained from Management
Cable Info Access (MCIA) register by specifying the thresholds offsets
within module EEPROM layout. This data does not pass validation and in
some cases can be unreliable. For example, due to some problem with the
module.

Add support for a new feature provided by Management Temperature (MTMP)
register for sanitization of temperature thresholds values.

Extend mlxsw_env_module_temp_thresholds_get() to get temperature
thresholds through MTMP field 'max_operational_temperature' - if it is
not zero, feature is supported. Otherwise fallback to old method and get
the thresholds through MCIA.

Signed-off-by: Mykola Kostenok <c_mykolak@nvidia.com>
Acked-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>