iio: adc: mp2629: fix potential array out of bound access

Add sentinel at end of maps to avoid potential array out of
bound access in iio core.

Fixes: 7abd9fb64682 ("iio: adc: mp2629: Add support for mp2629 ADC driver")
Signed-off-by: Saravanan Sekar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/adc/mp2629_adc.c

···
 	MP2629_MAP(SYSTEM_VOLT, "system-volt"),
 	MP2629_MAP(INPUT_VOLT, "input-volt"),
 	MP2629_MAP(BATT_CURRENT, "batt-current"),
-	MP2629_MAP(INPUT_CURRENT, "input-current")
+	MP2629_MAP(INPUT_CURRENT, "input-current"),
+	{ }
 };
 
 static int mp2629_read_raw(struct iio_dev *indio_dev,