PCI: kirin: Add HiSilicon Kirin SoC PCIe controller driver

Hisilicon PCIe driver shares the common functions for PCIe dw-host.

The poweron functions are developed on hi3660 SoC, while other functions
are common for Kirin series SoCs.

Low power mode (L1 sub-state and Suspend/Resume), hotplug and MSI feature
are not supported currently.

Signed-off-by: Xiaowei Song <songxiaowei@hisilicon.com>
[bhelgaas: fold in MAINTAINERS update from
http://lkml.kernel.org/r/20170704021516.96575-1-songxiaowei@hisilicon.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jingoo Han <jingoohan1@gmail.com>
Cc: Guodong Xu <guodong.xu@linaro.org>