If we only enable one of `CONFIG_NET_ARP_SEND` and
`CONFIG_NET_ICMPv6_NEIGHBOR`, both IPv4 and IPv6 traffic will send
ARP or NDP, which causes problem.
Example:
`CONFIG_NET_ARP_SEND=n`
`CONFIG_NET_ICMPv6_NEIGHBOR=y`
Wrong:
IPv4 traffic (`PF_INET`) goes into `icmpv6_neighbor`, which
definitely causes problem.
Correct:
IPv4 traffic doesn't call anything, IPv6 traffic calls `icmpv6_neighbor`
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
688f0e9117