thermal/drivers/hisi: Add platform prefix to function name

As the next patches will provide support for the hikey3660's sensor,
several functions with the same purpose but for different platforms will
be introduced.

In order to make a clear distinction between them, let's prefix the
function names with the platform name.

This patch has no functional changes, only name changes.

Signed-off-by: Kevin Wangtao <kevin.wangtao@linaro.org>
Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org> # hikey6220
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>