thermal/drivers/hisi: Rename and remove unused field

Rename the 'sensors' field to 'sensor' as we describe only one sensor.
Remove the 'sensor_temp' as it is no longer used.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>