At least on x86 on Bay and Cherry Trail devices the pmw-lpss modules must
be in the initrd too, otherwise the i915 driver will still load, but
it will report the following error:
[drm:pwm_setup_backlight [i915]] *ERROR* Failed to own the pwm chip
And not register /sys/class/backlight/intel_backlight and users will
not be able to control their backlight.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>