arm64: dts: qcom: msm8916: Add RPM sleep stats

MSM8916 is similar to the other SoCs that had the RPM stats node added
in commit 290bc684 ("arm64: dts: qcom: Enable RPM Sleep stats").
However, the dynamic offset readable at 0x14 seems only available on
some of the newer firmware versions. To be absolutely sure, make use
of the new qcom,msm8916-rpm-stats compatible that reads the sleep stats
from a fixed offset of 0xdba0.

Statistics are available for a "vmin" and "xosd" low power mode:

$ cat /sys/kernel/debug/qcom_stats/vmin
Count: 0
Last Entered At: 0
Last Exited At: 0
Accumulated Duration: 0
Client Votes: 0x0
$ cat /sys/kernel/debug/qcom_stats/xosd
Count: 0
Last Entered At: 0
Last Exited At: 0
Accumulated Duration: 0
Client Votes: 0x0

Cc: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211119213953.31970-4-stephan@gerhold.net