arm64: dts: qcom: sm6125-seine: Include PM6125 and configure PON

The Sony Xperia Seine board uses the PM6125; include it and configure
the PON buttons that provide the power and volume-up key.

Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220926190148.283805-5-marijn.suijten@somainline.org