dt-bindings: hwmon: ti,ina2xx: Add ti,shunt-gain property

dt-bindings: hwmon: ti,ina2xx: Add ti,shunt-gain property

Add a property to the binding to define the selected shunt voltage gain.
This specifies the range and accuracy that applies to the shunt circuit.
This property only applies to devices that have a selectable shunt
voltage range via PGA or ADCRANGE register configuration.

Signed-off-by: Nathan Rossi <nathan.rossi@digi.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211102052754.817220-2-nathan@nathanrossi.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>