dt-bindings: nfc: nxp,pn532: convert to dtschema

Convert the NXP PN532 NFC controller to DT schema format.

Drop the "clock-frequency" property during conversion because it is a
property of I2C bus controller, not I2C slave device.  It was also never
used by the driver.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211011073934.34340-4-krzysztof.kozlowski@canonical.com


Signed-off-by: Rob Herring <robh@kernel.org>