dt-bindings: pinctrl: convert controller description to the json-schema

This helps validating DTS and writing YAML files.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211110165720.30242-1-zajec5@gmail.com


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