dt-bindings: arm: at91: add lan966 pcb8385 board

Add documentation for Microchip LAN9668 PCB8385

Acked-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Link: https://lore.kernel.org/r/20251208083545.3642168-2-horatiu.vultur@microchip.com
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>

Author: HoratiuVultur

Documentation/devicetree/bindings/arm/atmel-at91.yaml

@@ -235,9 +235,11 @@ properties:
           - const: microchip,lan9662
           - const: microchip,lan966
 
-      - description: Microchip LAN9668 PCB8290 Evaluation Board.
+      - description: Microchip LAN9668 Evaluation Board.
         items:
-          - const: microchip,lan9668-pcb8290
+          - enum:
+              - microchip,lan9668-pcb8290
+              - microchip,lan9668-pcb8385
           - const: microchip,lan9668
           - const: microchip,lan966