layer.conf: Mark opkg-utils as ABISAFE for update-alternatives usage
Currently linux-firmware rebuilds for each machine due to its usage of
update-alternatives which in turn means a dependency on opkg-utils.
Marking opkg-utils as ABISAFE is the only option we have right now
to avoid this.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org> Signed-off-by: Steffen Sledz <sledz@dresearch-fe.de> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
