dt-bindings: interconnect: qcom,msm8998-bwmon: Resolve MSM8998 support

BWMONv4 has two sets of registers: one for handling the monitor itself
and one called "global" which hosts some sort of a headswitch and an
interrupt control register. We did not handle that one before, as on
SoCs starting with SDM845 they have been merged into a single contiguous
range.

To make the qcom,msm8998-bwmon less confusing and in preparation for
actual MSM8998 support, describe the global register space and introduce
new "qcom,sdm845-cpu-bwmon" compatible while keeping the
"qcom,sdm845-bwmon" as a fallback for SoCs with this merged register space
scheme.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230304-topic-ddr_bwmon-v3-1-77a050c2fbda@linaro.org
Signed-off-by: Georgi Djakov <djakov@kernel.org>