RDMA/i40iw: Handle workqueue allocation failure

alloc_ordered_workqueue may fail and return NULL.  The fix captures the
failure and handles it properly to avoid potential NULL pointer
dereferences.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Reviewed-by: Shiraz, Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/i40iw/i40iw.h

@@ -552,7 +552,7 @@ enum i40iw_status_code i40iw_obj_aligned_mem(struct i40iw_device *iwdev,
 
 void i40iw_request_reset(struct i40iw_device *iwdev);
 void i40iw_destroy_rdma_device(struct i40iw_ib_device *iwibdev);
-void i40iw_setup_cm_core(struct i40iw_device *iwdev);
+int i40iw_setup_cm_core(struct i40iw_device *iwdev);
 void i40iw_cleanup_cm_core(struct i40iw_cm_core *cm_core);
 void i40iw_process_ceq(struct i40iw_device *, struct i40iw_ceq *iwceq);
 void i40iw_process_aeq(struct i40iw_device *);