fff-network: rework sysctl's

Just disable autoconf.

Some sysctl's are currently not available due some missing kernel
features. Maybe some day they reappear.

Signed-off-by: Tim Niemeyer <tim@tn-x.org>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Christian Dresel <fff@chrisi01.de>
Tested-by: Christian Dresel <fff@chrisi01.de>