dt-bindings: arm: AT91: document EV23X71A board

Microchip EV23X71A board is an LAN9696 based evaluation board.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Link: https://lore.kernel.org/r/20260302112153.464422-6-robert.marko@sartura.hr
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>

Author: robimarko

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

@@ -243,6 +243,12 @@ properties:
           - const: microchip,lan9668
           - const: microchip,lan966
 
+      - description: Microchip LAN9696 EV23X71A Evaluation Board
+        items:
+          - const: microchip,ev23x71a
+          - const: microchip,lan9696
+          - const: microchip,lan9691
+
       - description: Kontron KSwitch D10 MMT series
         items:
           - enum: