dt-bindings: PCI: mediatek-gen3: Add mediatek,pbus-csr phandle array property

dt-bindings: PCI: mediatek-gen3: Add mediatek,pbus-csr phandle array property

Introduce the mediatek,pbus-csr property for the pbus-csr syscon node
available on EN7581 SoC.

The Airoha pbus-csr block provides a configuration interface for the
PBUS controller used to detect if a given address is accessible on PCIe
controller.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/20250225-en7581-pcie-pbus-csr-v4-1-24324382424a@kernel.org
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>