commit `Implement new backlight_level_params structure` breaks backlight

Commit 38077562e0594a294eaf4d8e6bbd8c1c26c2540f in kernel main branch breaks the backlight on my ASUS GA605W laptop, making it stuck at maximum brightness.

On advice from Mario I updated the dcn_3_5_1_dmcub.bin from firmware git, but this made no difference.

The problematic commit was found by kernel bisect and once reverted the backlight works fine.