thermal: hisilicon: fix for dependency

The thermal driver is standalone driver which is used to enable
thermal sensors, so it can be used with any cooling device and
should not bind with CPU cooling device driver.

This original patch is suggested by Amit Kucheria; so it's to
polish the dependency in Kconfig, and remove the dependency with
CPU_THERMAL.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>