dt-bindings: PCI: ti,j721e-pci-host: Simplify 'device-id' schema

'device-id' is just a scalar value, so just 'enum' is sufficient.

Link: https://lore.kernel.org/r/20230125221432.3058405-1-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>