Backport commit b7363e67 to stable 4.9.y

["Raju Rangoju" <rajur@xxxxxxxxxxx>]

Hi Greg,

Could you please backport the below commit to 4.9 stable tree. With a CPU bounded workqueue we see much lower cpu utilization and the same IOPs performance. 

commit b7363e67b23e04c23c2a99437feefac7292a88bc
Author: Sagi Grimberg <sagi@xxxxxxxxxxx>
Date:   Wed Mar 8 22:03:17 2017 +0200

    IB/device: Convert ib-comp-wq to be CPU-bound

Thanks,
Raju