sctp: reduce indent level in sctp_copy_local_addr_list

This patch is to reduce indent level by using continue when the addr
is not allowed, and also drop end_copy by using break.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>