dt-bindings: PCI: dwc: Apply common schema to Rockchip DW PCIe nodes

As the DT-bindings description states the Rockchip PCIe controller is
based on the DW PCIe RP IP-core thus its DT-nodes are supposed to be
compatible with the common DW PCIe controller schema. Let's make sure they
are evaluated against it by referring to the snps,dw-pcie.yaml schema in
the allOf sub-schemas composition.

Link: https://lore.kernel.org/r/20221113191301.5526-14-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>