dt-bindings: arm: add sam9x75 curiosity board

Add documentation for SAM9X75 Curiosity board.

Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Link: https://lore.kernel.org/r/20241010120438.93201-1-varshini.rajendran@microchip.com
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>

Author: varshini-rajendran

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

@@ -106,6 +106,12 @@ properties:
           - const: microchip,sam9x60
           - const: atmel,at91sam9
 
+      - description: Microchip SAM9X7 Evaluation Boards
+        items:
+          - const: microchip,sam9x75-curiosity
+          - const: microchip,sam9x7
+          - const: atmel,at91sam9
+
       - description: Nattis v2 board with Natte v2 power board
         items:
           - const: axentia,nattis-2