dt-bindings: PCI: pci-rcar-gen2: Add device tree support for r8a7742

Add internal PCI bridge support for r8a7742 SoC. The Renesas RZ/G1H
(R8A7742) internal PCI bridge is identical to the R-Car Gen2 family.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marian-Cristian Rotariu <marian-cristian.rotariu.rb@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>