dt-bindings: touchscreen: convert bu21013 bindings to json schema

dt-bindings: touchscreen: convert bu21013 bindings to json schema

Convert Rohm BU21013 I2C touchscreen controller device tree binding to
json-schema.

Additional changes:
- Replace <supply_name>-supply with avdd-supply to match example and
  existing DTS.
- Add reset-gpios in the example because it is required.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250918153630.2535208-1-dario.binacchi@amarulasolutions.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>