linux: Switch to kernel version check to determine if sysfs can relate devs
We rely on the kernel version for determining capabilities, except for
sysfs_can_relate_devices. This changes sysfs_can_relate_devices over to
a kernel version check to.
This makes things more consistent, removes a whole bunch of code, and since
it stops us from needlessly banging sysfs, it reduces the avarage run time for
the stress test on my system from 21.8 to 16.7 seconds.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>