dt-bindings: soc: qcom: stats: Document SDM845 compatible

SDM845 is a special case compared to the other platforms that use RPMh
stats, since it only has 2 stats (aosd and cxsd), while the others have
a 3rd one (ddr).

So in order for the driver to use the dedicated stats config, we added
the SDM845 dedicated compatible, which we document here.

Signed-off-by: Abel Vesa <[e-mail]>
Acked-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/soc/qcom/qcom-stats.yaml

···
   compatible:
     enum:
       - qcom,rpmh-stats
+      - qcom,sdm845-rpmh-stats
       - qcom,rpm-stats
       # For older RPM firmware versions with fixed offset for the sleep stats
       - qcom,apq8084-rpm-stats