Adding RTC battery voltage sensor to SDR list

[nv-ynissan]

Sensor name is "rtc_voltage". Sensor is discrete with two value, 0x0 and 0x80, which correspond to expected and low voltage, respectively. The values are mapped to their corresponding voltage values, 3V and 2V, respectively, so they can be represented as a non-discrete sensor (supported by the Redfish schema). A critical lower threshold is set in 2.3V to allow assertion in case of low voltage.

Test 1:
# ipmitool -I ipmb sensor

...
rtc_voltage      | 3.000      | Volts      | ok    | na        | 2.300     | na        | na        | na

Test 2:
# ipmitool sensor

...
rtc_voltage      | 3.000      | Volts      | ok    | na        | 2.302     | na        | na        | na

Test 3:
# curl -k -u <USERNAME>:<PASSWORD> -H "Content-Type: application/json" -X GET https://<BMC_IP>/redfish/v1/Chassis/Card1/Sensors

{
    "@odata.id": "/redfish/v1/Chassis/Card1/Sensors",
    "@odata.type": "#SensorCollection.SensorCollection",
    "Description": "Collection of Sensors for this Chassis",
    "Members": [
        ...
        {
            "@odata.id": "/redfish/v1/Chassis/Card1/Sensors/rtc_voltage"
        }
    ],
    "[email protected]": 21,
    "Name": "Sensors"
}

Test 4:
# curl -k -u <USERNAME>:<PASSWORD> -H "Content-Type: application/json" -X GET https://<BMC_IP>/redfish/v1/Chassis/Card1/Sensors/rtc_voltage

{
    "@odata.id": "/redfish/v1/Chassis/Card1/Sensors/rtc_voltage",
    "@odata.type": "#Sensor.v1_7_0.Sensor",
    "Id": "rtc_voltage",
    "Name": "rtc voltage",
    "Reading": 3.0,
    "ReadingRangeMax": 3.0,
    "ReadingRangeMin": 2.0,
    "ReadingType": "Voltage",
    "ReadingUnits": "V",
    "RelatedItem": [
        {
            "@odata.id": "/redfish/v1/Systems/Bluefield"
        }
    ],
    "Status": {
        "Conditions": [],
        "Health": "OK",
        "HealthRollup": "OK",
        "State": "Enabled"
    },
    "Thresholds": {
        "LowerCritical": {
            "Reading": 2.3
        }
    }
}

Fixes jira https://redmine.mellanox.com/issues/4016381

Signed-off-by: Yuval Nissan [email protected]