thermal: uniphier: Convert to SPDX identifier

This converts license boilerplate to SPDX identifier, and removes
unnecessary lines.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>