dt-bindings: cpu: Add a support cpu type for cortex-a55

Add arm cpu type cortex-a55.
Signed-off-by: james.tai <james.tai@realtek.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/cpus.yaml

@@ -124,6 +124,7 @@ properties:
       - arm,cortex-a15
       - arm,cortex-a17
       - arm,cortex-a53
+      - arm,cortex-a55
       - arm,cortex-a57
       - arm,cortex-a72
       - arm,cortex-a73