dt-bindings: hwmon: ti,ina2xx: Document ti,ina238 compatible string

Document the compatible string for the Texas Instruments INA238, this
device is a variant of the existing INA2xx devices and has the same
device tree bindings (shunt resistor).

Signed-off-by: Nathan Rossi <nathan.rossi@digi.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211102052754.817220-1-nathan@nathanrossi.com


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