arm64: dts: qcom: sc7280-idp: add amp pin config function

arm64: dts: qcom: sc7280-idp: add amp pin config function

Bindings expect each pin config to come with a "function" property:

  sc7280-crd-r3.dtb: pinctrl@f100000: amp-en-state: 'oneOf' conditional failed, one must be fixed:
    'function' is a required property
    'bias-pull-down', 'drive-strength', 'pins' do not match any of the regexes: '-pins$', 'pinctrl-[0-9]+'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221230135645.56401-9-krzysztof.kozlowski@linaro.org