arm64: dts: qcom: sa8775p: add cpufreq node

Add a node for the cpufreq engine and specify the frequency domains for
all CPUs.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230221150543.283487-3-brgl@bgdev.pl