phy: HiSilicon: Add driver for Kirin 970 PCIe PHY

The Kirin 970 PHY is somewhat similar to the Kirin 960, but it
does a lot more. Add the needed bits for PCIe to start working on
HiKey 970 boards.

Co-developed-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/b7a4ff41b57d861b003f1a00cae81f3d226fbe18.1632814194.git.mchehab+huawei@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>