Avoid creating non-working backlight sysfs knob from ASUS board

[Kai-Heng Feng]

[Impact]
Backlight sysfs knobs created by asus-wmi don't really work, hence
systemd-backlight services are in failed state.

[Fix]
Ensure the backlight device are really present

[Test]
With the fix applied, the backlight sysfs knobs are not longer present
under /sys/class/backlight, so there's no more failed systemd-backlight
service.

[Where problems could occur]
Though highly unlikely, but if there's working device that is created
even when the WMI read is 0xffffffff, the device will be missing.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux/6.8.0-32.32 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-noble-linux' to 'verification-done-noble-linux'. If the problem still exists, change the tag 'verification-needed-noble-linux' to 'verification-failed-noble-linux'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux/5.15.0-111.121 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux' to 'verification-done-jammy-linux'. If the problem still exists, change the tag 'verification-needed-jammy-linux' to 'verification-failed-jammy-linux'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!