dt-bindings: PCI: ti,j721e-pci-host: add interrupt controller definition

dt-bindings: PCI: ti,j721e-pci-host: add interrupt controller definition

Add missing 'interrupt-controller' property and related subnodes to resolve
the following warning:

arch/arm64/boot/dts/ti/k3-j721s2-common-proc-board.dtb: pcie@2910000: Unevaluated properties are not allowed ('interrupt-controller' was unexpected)
        From schema: Documentation/devicetree/bindings/pci/ti,j721e-pci-host.yaml

Link: https://lore.kernel.org/r/20221025081909.404107-2-mranostay@ti.com
Signed-off-by: Matt Ranostay <mranostay@ti.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>