bindings: PCI: artpec: Add support for the ARTPEC-7 SoC

Add support for the ARTPEC-7 SoC in the artpec6 driver.
The ARTPEC-6 SoC and the ARTPEC-7 SoC are very similar.
Unfortunately, some fields in the PCIECFG and PCIESTAT
register have changed.
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/axis,artpec6-pcie.txt

@@ -6,6 +6,8 @@ and thus inherits all the common properties defined in designware-pcie.txt.
 Required properties:
 - compatible: "axis,artpec6-pcie", "snps,dw-pcie" for ARTPEC-6 in RC mode;
 	      "axis,artpec6-pcie-ep", "snps,dw-pcie" for ARTPEC-6 in EP mode;
+	      "axis,artpec7-pcie", "snps,dw-pcie" for ARTPEC-7 in RC mode;
+	      "axis,artpec7-pcie-ep", "snps,dw-pcie" for ARTPEC-7 in EP mode;
 - reg: base addresses and lengths of the PCIe controller (DBI),
 	the PHY controller, and configuration address space.
 - reg-names: Must include the following entries: