[Bug]ipmitool sensor cannot present correct values

[justin0309]

When I set CRITLO_temp1 to negative numbers in the conf under phosphor-hwmon, the correct values ​​are displayed on dbus, but values ​​less than 0 cannot be displayed through the ipmitool sensor.
The result of my own experiment is that when the value is less than 0, it will be set to 0.

In addition, I set the values ​​of MINVALUE_temp1 and MAXVALUE_temp1 but non-Recoverable still shows NA.

Because our temperature threshold supports negative numbers, it seems that it is because the type of param lowerCritical is uint8_t. Even if the type set in ipmi sensor.yaml is double, no negative numbers will be generated.
[ * @param lowerCritical - Lower critical threshold](https://github.com/openbmc/phosphor-host-ipmid/blob/68d9d40530351e3f3db2c00a25969b0efc9fbe3f/sensorhandler.cpp#L787)](https://github.com/openbmc/phosphor-host-ipmid/blob/68d9d40530351e3f3db2c00a25969b0efc9fbe3f/sensorhandler.cpp#L787)