Add combo phy driver for HiSilicon STB SoCs. This phy can be
used as pcie-phy, sata-phy or usb-phy.

Changes for v5:
 - Add bindings doc for Hi3798CV200 peripheral controller, and refer to
   the bindings of this parent node in combphy bindings doc.

Changes for v4:
 - Instead of relying on device id, add a new property
   hisilicon,fixed-mode for combphy device that doesn't support mode
   select but a fixed phy mode.
 - Move combphy mode select register bits definition to device tree, as
   it may vary from one device to another.

Changes for v3:
 - Make combphy device be child of peripheral controller and use 'reg'
   property for mapping combphy configuration registers.
 - Kill "hisilicon,peripheral-syscon" property, since parent node is
   just the syscon controller now.
 - Check combphy id to handle the quirk that combphy0 can not configure
   mode but always works in USB3 mode.
 - Unify phy .init and .exit hooks for different combphy instances and
   work modes, as the only quirk we need to handle is that combphy0 can
   only work in USB3 mode.
 - Better naming for clock and reset, 'ref' to 'ref_clk', 'por' to
   'por_rst'.

Changes for v2:
 - Move DT bindings into a separate patch.
 - Drop the spurious newline from drivers/phy/Makefile.
 - Use the phy type defines in dt-bindings/phy/phy.h.
 - Use PTR_ERR_OR_ZERO() for checking return from
   devm_of_phy_provider_register().
 - Add USB3 phy support.
Signed-off-by: Jianguo Sun <sunjianguo1@huawei.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>