The binding reference common cdns-pcie-host.yaml, which already defines
msi-parent and has a reference to pci-bus.yaml schema.  Drop redundant
pieces here to make it a bit smaller.

Link: https://lore.kernel.org/linux-pci/20240413151617.35630-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>