dt-bindings: altera: Add Chameleon v3 board

Add Mercury+ AA1 boards category, together with the Chameleon v3 board.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Paweł Anikiel <pan@semihalf.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>