dt-bindings: pinctrl: convert semtech,sx150xq bindings to dt-schema

This converts the Semtech SX150Xq bindings to dt-schemas, add necessary
bindings documentation to cover all differences between HW variants
and current bindings usage.

Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221005-mdm9615-sx1509q-yaml-v3-0-e8b349eb1900@linaro.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>