dt-bindings: arm: qcom: document AL02-C6 board based on IPQ9574 family

Document AL02-C6 (Reference Design Platform 449) board based on IPQ9574
family of SoCs.

Signed-off-by: Devi Priya <quic_devipriy@quicinc.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230516135013.3547-2-quic_devipriy@quicinc.com