reset: hisilicon: add reset controller driver for hisilicon SOCs

In most of hisilicon SOCs, reset controller and clock provider are
combined together as a block named CRG (Clock and Reset Generator).
This patch mainly implements the reset function.

Signed-off-by: Jiancheng Xue <xuejiancheng@hisilicon.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>