CVE-2026-98664: iio: imu: adis16400: fix unprotected debugfs reads

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

iio: imu: adis16400: fix unprotected debugfs reads

adis16400serialnumberfops is open coded and never calls debugfsfileget(), so debugfsremoverecursive() does not wait for a read in progress and unbind frees the iiodev underneath it.

Commit ae1d37a9bb4b ("iio: imu: adis16400: use DEFINEDEBUGFSATTRIBUTE instead of DEFINESIMPLEATTRIBUTE") converted productid and flashcount to DEFINEDEBUGFSATTRIBUTE, which protects itself, but moved all three files to debugfscreatefileunsafe().

serialnumber prints three registers as "%.4x-%.4x-%.4x" and DEFINEDEBUGFSATTRIBUTE() formats a single u64, so it cannot be converted without changing what the file returns. adis16475 and adis16550 already use debugfscreatefile() for their open coded files. Use it here too.