dt-bindings: mfd: qcom-spmi-pmic: Add pm6125 compatible

Document support for the pm6125, typically paired with the sm6125 SoC.

Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220926190148.283805-2-marijn.suijten@somainline.org