The devices can be created at run-time for quite some time already and the
load-time device creation collides with attempts to create the device of
the same name:
# rmmod ifb
# ip link add ifb0 type ifb
RTNETLINK answers: File exists
This is pretty much the same situation as was with the block loop devices
which was solved by adding a build-time configuration that the
distributions could use as they deem fit while keeping the default for
compatibility.
Let's do that here as well.
Signed-off-by: Lubomir Rintel <lkundrak@xxxxx>