Improve driver temperature reporting when using TMC2240 drivers

[dc42]

For the TOOL1RR we currently base the temperature reported by the "drivers" temperature sensor on whether the driver is reporting over temperature warning or error using the same coder that we use for other drive types. However, we fetch the actual temperature from the driver, so we should use that value instead. This also has implications for future Duet3D boards that use TMC2240 drivers, ir future TMC drivers that report actual temperature.

See also #1184.