dt-bindings: mfd: qcom-pm8xxx: Add missing child nodes

Add gpio, keypad, led, mpps, pwrkey, vibrator and xoadc as possible
child nodes of qcom,pm8xxx, referencing existint schema files.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230827132525.951475-3-dmitry.baryshkov@linaro.org


Signed-off-by: Lee Jones <lee@kernel.org>