iio: adc: axp20x_adc: make axp717_maps const

Add const qualifier to struct iio_map axp717_maps[]. This is read-only
data so it can be made const.

Signed-off-by: David Lechner <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/axp20x_adc.c

···
 	{ }
 };
 
-static struct iio_map axp717_maps[] = {
+static const struct iio_map axp717_maps[] = {
 	{
 		.consumer_dev_name = "axp20x-usb-power-supply",
 		.consumer_channel = "vbus_v",