Add a HiSilicon STB SoC PCIe controller driver.  This controller is based
on the DesignWare PCIe core.
Signed-off-by: NJianguo Sun <sunjianguo1@huawei.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>