Exclude third party kernel module for initrd

[ragazenta]

Hi,

In my case, I use 8821au.ko kernel module for TP-Link USB Wireless dongle. I manually compiled it from here.
I put it to mkosi.extras/usr/lib/modules/<version>/kernel/drivers/net/wireless/8821au.ko.

After this commit a90850c, I got error when building default initrd.

‣  Running modinfo to fetch kernel module dependencies
modinfo: ERROR: Module 8821au not found.

I thought I could use KernelModulesInitrdExclude=8821au, but still error.

Revert that commit a90850c solved my issue though.

[DaanDeMeyer]

@ragazenta Please give #2301 a try and let me know if that fixes the issue