power: reset: move hisilicon reboot code

Move reboot code from hisilicon platform driver into reset driver.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Acked-by: Wei Xu <xuwei5@hisilicon.com>
Signed-off-by: Olof Johansson <olof@lixom.net>