Fixed: FAI client installation gets stuck with message "i915 [drm] VT-d active for gfx access"

[Samadhan Fuke]

We have identified and fixed an issue where the FAI client
installation gets stuck with the message: `i915 0000:00:02.0 [drm]
VT-d active for gfx access`.

We have observed this screen lockup issue specifically on machines
equipped with Intel CPUs with Integrated iGPU Intel® UHD Graphics.
This occurs due to a conflict with the i915 driver, causing the
graphics system to freeze during installation. When initiating network
installation on FAI clients' barebone machines with Intel CPUs and
Integrated iGPU Intel® UHD Graphics, booting with the latest kernel
version (after 6.1), the i915 driver issue results in the screen
becoming stuck, preventing users from proceeding with the FAI profile
selection, etc.

Here are references for similar issues:
- [OpenWRT Forum](https://forum.openwrt.org/t/silly-little-i915-issue-on-x86/150405)
- [TrueNAS Community](https://www.truenas.com/community/threads/alder-lake-gpu-enablement-not-working.108651/)
- [Unraid Forum](https://forums.unraid.net/topic/140660-fresh-usb-booting-stuck-at-i915-000000020-drm-vt-d-active-for-gfx-access-any-ideas/)

Solution:
To resolve this issue in FAI, modify the kernel boot parameter to
disable the UHD graphics driver mode setting.

Add `i915.modeset=0` as a kernel boot parameter while booting the
latest Linux kernel 6.5 and above to configure FAI for PXE boot.
Update the file `/srv/tftp/fai/pxelinux.cfg/default` as shown below:

Complete Example of the Updated File:
```
/srv/tftp/fai/pxelinux.cfg/default

default fai-generated
label fai-generated
kernel vmlinuz-6.5.0-0.deb12.4-amd64
# generated by fai-chboot for host default with IP no IP
append initrd=initrd.img-6.5.0-0.deb12.4-amd64 i915.modeset=0 ip=dhcp
root=192.168.1.100:/srv/fai/nfsroot:vers=3 rootovl
FAI_FLAGS=verbose,sshd,createvt,menu,reboot
FAI_CONFIG_SRC=nfs://192.168.1.100//srv/fai/config FAI_ACTION=install
```

Best regards,
Samadhan