dt-bindings: pinctrl: qcom,ipq6018: add qpic_pad function

The IPQ6018 pinctrl driver supports qpic_pad and DTS already uses it:

  'qpic_pad' is not one of ['adsp_ext', 'alsp_int', 'atest_bbrx0', ...

Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221016170035.35014-9-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>