iio: adc: axp20x_adc: Add missing sentinel to AXP717 ADC channel maps

The AXP717 ADC channel maps is missing a sentinel entry at the end. This
causes a KASAN warning.

Add the missing sentinel entry.

Fixes: 5ba0cb92 ("iio: adc: axp20x_adc: add support for AXP717 ADC")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Link: https://patch.msgid.link/20250607135627.2086850-1-wens@kernel.org


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>