arm64: dts: qcom: sdm845: Use the correct BWMON compatible

Drop the incorrect msm8998 fallback and use the new qcom,sdm845-cpu-bwmon
compatible to distinguish the CPU BWMON found on this platform.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230304-topic-ddr_bwmon-v3-6-77a050c2fbda@linaro.org