hwmon: shtc1: add support for device tree bindings

Add support for DTS bindings for the sensirion shtc1,shtw1 and shtc3.

Signed-off-by: Chris Ruehl <chris.ruehl@gtsys.com.hk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200815012227.32538-2-chris.ruehl@gtsys.com.hk
[groeck: Resolved conflicts]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>