RDMA/nes: Make unnecessarily global nes_set_pau() static

Warned about by sparse.

Signed-off-by: Tatyana Nikolova <Tatyana.E.Nikolova@intel.com>
Signed-off-by: Faisal Latif <Faisal.Latif@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>