dt-bindings: arm: amazon: add Amazon Annapurna Labs Alpine V3

This patch adds DT bindings info for Amazon Annapurna Labs Alpine V3.

Link: https://lore.kernel.org/r/20200724132654.16549-6-hhhawa@amazon.com
Signed-off-by: Hanna Hawa <hhhawa@amazon.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/arm/amazon,al.yaml

@@ -24,4 +24,10 @@ properties:
               - al,alpine-v2-evp
           - const: al,alpine-v2
 
+      - description: Boards with Alpine V3 SoC
+        items:
+          - enum:
+              - amazon,al-alpine-v3-evp
+          - const: amazon,al-alpine-v3
+
 ...