dt-bindings: PCI: brcm,stb-pcie: Add num-lanes property

Add optional num-lanes property Broadcom STB PCIe host controllers.

Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250530224035.41886-2-james.quinlan@broadcom.com

Author: jamesequinlan

Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml

@@ -107,6 +107,10 @@ properties:
       - const: bridge
       - const: swinit
 
+  num-lanes:
+    default: 1
+    maximum: 4
+
 required:
   - compatible
   - reg