RDMA/rdmavt: Fix error code in rvt_create_qp()

Return negative -ENOMEM instead of positive ENOMEM.  Returning a postive
value will cause an Oops because it becomes an ERR_PTR() in the
create_qp() function.

Fixes: 514aee66 ("RDMA: Globally allocate and release QP memory")
Link: https://lore.kernel.org/r/20211013080645.GD6010@kiliSigned-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rdmavt/qp.c

@@ -1223,7 +1223,7 @@ int rvt_create_qp(struct ib_qp *ibqp, struct ib_qp_init_attr *init_attr,
 	spin_lock(&rdi->n_qps_lock);
 	if (rdi->n_qps_allocated == rdi->dparms.props.max_qp) {
 		spin_unlock(&rdi->n_qps_lock);
-		ret = ENOMEM;
+		ret = -ENOMEM;
 		goto bail_ip;
 	}