IB/ipoib: Fix for notify send CQ failure messages

If IB_CQ_REPORT_MISSED_EVENTS flag is passed in ib_req_notify_cq()
it may return positive value indicating non-empty CQ.
If return code not verified the log might be flooded with false
warning messages "request notify on send CQ failed".

Fixes: 8966e28d ("IB/ipoib: Use NAPI in UD/TX flows")
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>