dt-bindings: arm: qcom: document AL02-C9 board based on IPQ9574 family

Document AL02-C9 (Reference Design Platform 454) board based on IPQ9574
family of SoCs.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Poovendhan Selvaraj <quic_poovendh@quicinc.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230531032648.23816-2-quic_poovendh@quicinc.com