dt-bindings: extcon: ptn5150: Convert binding to DT schema

Convert the ptn-5150 extcon driver bindings to DT schema format using
json-schema.  The differences with original bindings document:
 - Use "gpios" suffix for the "int" and "vbus" gpio,
 - Skip generic "pinctrl" property as it is not really required.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Vijai Kumar K <vijaikumar.kanagarajan@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>