package: fold the IPv6 menu into Network

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36634 3c298f89-4303-0410-b956-a3cf2f4a3e73
packages: fold the IPv6 menu into Network

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@36635 3c298f89-4303-0410-b956-a3cf2f4a3e73