iio: health: afe4403: Fix oob read in afe4403_read_raw

In the Linux kernel, the following vulnerability has been resolved:

iio: health: afe4403: Fix oob read in afe4403_read_raw

KASAN report out-of-bounds read as follows:

BUG: KASAN: global-out-of-bounds in afe4403_read_raw+0x42e/0x4c0

Read of size 4 at addr ffffffffc02ac638 by task cat/279

Call Trace:

afe4403_read_raw

iio_read_channel_info

dev_attr_show

The buggy address belongs to the variable:

afe4403_channel_leds+0x18/0xffffffffffffe9e0

This issue can be reproduced by singe command:

$ cat /sys/bus/spi/devices/spi0.0/iio\:device0/in_intensity6_raw

The array size of afe4403_channel_leds is less than channels, so access

with chan->address cause OOB read in afe4403_read_raw. Fix it by moving

access before use it.