package/fff: add ip-full to variant layer3

"ip" is one of the most essential tools on a gateway. At the moment
there is only one dependency to the metapackage ip from the nodewatcher,
which pulls ip-tiny. Dropping the nodewatcher causes a fallback to the
busybox built-in ip-command.

Signed-off-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Fabian Bläse <fabian@blaese.de>
[fabian@blaese.de: rebase onto master]
Signed-off-by: Fabian Bläse <fabian@blaese.de>