devfreq is being handled differently on our kernels. With 5.6+ frequency
is switched automatically by the kernel for devfreq, when the powersave
governor is set. So in that case we only to that (done by udev in the future).

This also makes devfreq settings compatible with the devkit again because
it reads the minimum frequency which is different than on the phone,
from sysfs.

Also, we particularly handle 5.6-rc based kernel versions that
include a broken devfreq implementation / setup. starting with version
5.6.0 we need to increment the ABI version to 2.