dt-bindings: remoteproc: qcom: Introduce shutdown-ack irq for Q6V5

Introduce shutdown-irq binding required for sysmon shutdown for Q6V5 MSS
on SDM845/MSM8996 SoCs and for WCSS Q6V5 on QCS404 SoC.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>