arm64: dts: apq8096-db820c: Fix VDD core voltage

arm64: dts: apq8096-db820c: Fix VDD core voltage

APQ8096 has its VDD APC (Power for quad Kryo applications
microprocessors) powered by PM8996 PMIC S9, S10, S11 tri-phase
regulators (gang). The bootloader may have configured these
regulators with non sustainable default values, leading to sporadic
hangs under CPU stress tests (cpufreq-bench). Ideally we should enable
voltage scaling along with frequency scaling, but for now just set the
regulator gang value to a sane voltage, capable of supporting highest
frequencies (turbo).

Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Link: https://lore.kernel.org/r/1578401755-26211-1-git-send-email-loic.poulain@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>