RDMA/nes: Use more concise list_for_each_entry()

In list iteration code, you normally wouldn't be calling
"container_of()" directly anyway, you'd be invoking "list_entry()".
But you don't even need that here, "list_for_each_entry()" is fine.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Acked-by: Glenn Streiff <gstreiff@neteffect.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>