Add the mailbox compatible for IPQ9574 SoC.
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Devi Priya <quic_devipriy@quicinc.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>