ICMP's conn->dev is changing in icmp_sendmsg, when sending to different
address, or when error occurs (like NETDEV_DOWN). Then the poll callback
cannot be dropped from previous dev in free, because the dev is wrong.
So add dev to struct icmp_poll_s just like struct udp_poll_s.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>