PCI: rcar: Add gen2 fallback compatibility string for pci-rcar-gen2

Add fallback compatibility string for R-Car Gen 2 family.  This is in
keeping with the fallback scheme being adopted wherever appropriate for
drivers for Renesas SoCs.
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NRob Herring <robh@kernel.org>

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

@@ -8,7 +8,14 @@ OHCI and EHCI controllers.
 Required properties:
 - compatible: "renesas,pci-r8a7790" for the R8A7790 SoC;
 	      "renesas,pci-r8a7791" for the R8A7791 SoC;
-	      "renesas,pci-r8a7794" for the R8A7794 SoC.
+	      "renesas,pci-r8a7794" for the R8A7794 SoC;
+	      "renesas,pci-rcar-gen2" for a generic R-Car Gen2 compatible device
+
+
+	      When compatible with the generic version, nodes must list the
+	      SoC-specific version corresponding to the platform first
+	      followed by the generic version.
+
 - reg:	A list of physical regions to access the device: the first is
 	the operational registers for the OHCI/EHCI controllers and the
 	second is for the bridge configuration and control registers.
@@ -32,7 +39,7 @@ Optional properties:
 Example SoC configuration:
 
 	pci0: pci@ee090000  {
-		compatible = "renesas,pci-r8a7790";
+		compatible = "renesas,pci-r8a7790", "renesas,pci-rcar-gen2";
 		clocks = <&mstp7_clks R8A7790_CLK_EHCI>;
 		reg = <0x0 0xee090000 0x0 0xc00>,
 		      <0x0 0xee080000 0x0 0x1100>;

drivers/pci/host/pci-rcar-gen2.c

@@ -430,6 +430,7 @@ static int rcar_pci_probe(struct platform_device *pdev)
 }
 
 static struct of_device_id rcar_pci_of_match[] = {
+	{ .compatible = "renesas,pci-rcar-gen2", },
 	{ .compatible = "renesas,pci-r8a7790", },
 	{ .compatible = "renesas,pci-r8a7791", },
 	{ .compatible = "renesas,pci-r8a7794", },