Some tools may currently be using only the deprecated attribute;
let's print an elaborate and clear deprecation notice to kmsg.

To do that, we have to replace the whole sysfs file, since we inherit
the original one from netdev.
Signed-off-by: Arseny Maslennikov <ar@cs.msu.ru>
Signed-off-by: Doug Ledford <dledford@redhat.com>