dt-bindings: power: supply: axp20x: Add AXP192 compatible

The AXP192 is most similar to the AXP202, but the current
limits are different and the USB OTG status register has
a different address (0x04 instead of 0x02).

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>