hwmon: Add Synaptics AS370 PVT sensor driver

Add a new driver for Synaptics AS370 PVT sensors. Currently, only
temperature is supported.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190827113259.4fb64a17@xhacker.debian


Signed-off-by: Guenter Roeck <linux@roeck-us.net>