drivers/net/cnic.c: remove invalid reference to list iterator variable

drivers/net/cnic.c: remove invalid reference to list iterator variable

If list_for_each_entry, etc complete a traversal of the list, the iterator
variable ends up pointing to an address at an offset from the list head,
and not a meaningful structure.  Thus this value should not be used after
the end of the iterator.  There does not seem to be a meaningful value to
provide to netdev_warn.  Replace with pr_warn, since pr_err is used
elsewhere.

This problem was found using Coccinelle (http://coccinelle.lip6.fr/).

(cherry picked from commit 022f09784b85396b4ceba954ce28e50de4882281)
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Joe Jin <joe.jin@oracle.com>