thermal/drivers/hisi: Remove the multiple sensors support

By essence, the tsensor does not really support multiple sensor at the same
time. It allows to set a sensor and use it to get the temperature, another
sensor could be switched but with a delay of 3-5ms. It is difficult to read
simultaneously several sensors without a big delay.

Today, just one sensor is used, it is not necessary to deal with multiple
sensors in the code. Remove them and if it is needed in the future add them
on top of a code which will be clean up in the meantime.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Wangtao (Kevin, Kirin) <kevin.wangtao@hisilicon.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>