arm64: dts: qcom: Add PM6350 PMIC

PM6350 is used in SM6350 and provides similar functionality to other
Qualcomm PMICs.

Add the pon node with power & volume key and the gpios.

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Reviewed-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211007212444.328034-7-luca@z3ntu.xyz