team: fix port list dump for big number of ports

In case the port list dump does not fit into one skb currently the
dump would start over again. Fix this by continue from the last dumped
port.

Introduced by commit d90f889e

 (team: handle sending port list in the
same way option list is sent)

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>