hwmon: Add DT bindings schema for PVT controller

PVT controller (MR75203) is used to configure & control
Moortec embedded analog IP which contains temprature sensor(TS),
voltage monitor(VM) & process detector(PD) modules.

Add DT bindings schema for PVT controller.

Signed-off-by: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/b540b49ca47d75c5f716f8a4e4eed0664a1116bf.1601889876.git.rahul.tanwar@linux.intel.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>