thermal: mtk_thermal: Check return value of devm_thermal_zone_of_sensor_register

devm_thermal_zone_of_sensor_register can fail, so check it's return value.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>