dt-bindings: PCI: dwc: Add phys/phy-names common properties

It's normal to have the DW PCIe RP/EP DT-nodes equipped with the explicit
PHY phandle references. There can be up to 16 PHYs attach in accordance
with the maximum number of supported PCIe lanes. Let's extend the common
DW PCIe controller schema with the 'phys' and 'phy-names' properties
definition. There two types PHY names are defined: preferred generic names
'^pcie[0-9]+$' and non-preferred vendor-specific names
'^pcie([0-9]+|-?phy[0-9]*)?$' so to match the names currently supported by
the DW PCIe platform drivers ("pcie": meson; "pciephy": qcom, imx6;
"pcie-phy": uniphier, rockchip, spear13xx; "pcie": intel-gw; "pcie-phy%d":
keystone, dra7xx; "pcie": histb, etc).

Link: https://lore.kernel.org/r/20221113191301.5526-6-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>