When implementing IPv6-related logic, we found the `net_ipv6_pref2mask` and `net_ipv6addr_copy` are using different argument order: ``` net_ipv6addr_copy(ifaddr->addr, addr); net_ipv6_pref2mask(preflen, ifaddr->mask); ``` Change the order to: ``` net_ipv6addr_copy(ifaddr->addr, addr); net_ipv6_pref2mask(ifaddr->mask, preflen); ``` Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>