dt-bindings: PCI: rcar: Add device tree support for r8a7744

Add internal PCI bridge support for r8a7744 SoC. The Renesas RZ/G1N
(R8A7744) internal PCI bridge is identical to the R-Car Gen2 family.

This doesn't change the driver, so it does nothing by itself.  But it does
mean that checkpatch won't complain about a future patch that adds
"renesas,pci-r8a7744" to a DT, which helps ensure that shipped DTs use
documented compatibility strings.
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/pci/pci-rcar-gen2.txt

@@ -7,6 +7,7 @@ OHCI and EHCI controllers.
 
 Required properties:
 - compatible: "renesas,pci-r8a7743" for the R8A7743 SoC;
+	      "renesas,pci-r8a7744" for the R8A7744 SoC;
 	      "renesas,pci-r8a7745" for the R8A7745 SoC;
 	      "renesas,pci-r8a7790" for the R8A7790 SoC;
 	      "renesas,pci-r8a7791" for the R8A7791 SoC;