dt-bindings: soc: qcom: stats: Add QMP handle

The stats can be expanded by poking the Always-On Subsystem through QMP.
Allow passing a QMP handle for configurations that support it.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231130-topic-ddr_sleep_stats-v1-1-5981c2e764b6@linaro.org


Signed-off-by: Bjorn Andersson <andersson@kernel.org>