The Volume Down & Power buttons are controlled by the PMIC via
the PON hardware, and the Volume Up is connected to a PMIC gpio.

Enable the necessary hardware and setup the GPIO state for the
Volume Up gpio key.
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230525-topic-sm8550-upstream-pm8550-lpg-dt-v4-4-a288f24af81b@linaro.org