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

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

This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
This ID is fixed in Linux Kernel version v5.15.80 by commit 1678d4abb2dc2ca3b05b998a9d88616976e4f947, it was introduced in version v5.8 by commit 7abd9fb6468225f5c7f83149ce279cc1a912a68a. For more details please see the references link.