dt-bindings: ARM: at91: document sama7g5ek board

Document the SAMA7G5 Evaluation Kit based on sama7g5 SoC.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210628120452.74408-1-eugen.hristev@microchip.com

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

@@ -145,6 +145,11 @@ properties:
           - const: atmel,sama5d4
           - const: atmel,sama5
 
+      - items:
+          - const: microchip,sama7g5ek # SAMA7G5 Evaluation Kit
+          - const: microchip,sama7g5
+          - const: microchip,sama7
+
       - items:
           - enum:
               - atmel,sams70j19