RDS: RDMA: fix the ib_map_mr_sg_zbva() argument

Fixes warning: Using plain integer as NULL pointer
Signed-off-by: NSantosh Shilimkar <santosh.shilimkar@oracle.com>

net/rds/ib_frmr.c

@@ -104,14 +104,15 @@ static int rds_ib_post_reg_frmr(struct rds_ib_mr *ibmr)
 	struct rds_ib_frmr *frmr = &ibmr->u.frmr;
 	struct ib_send_wr *failed_wr;
 	struct ib_reg_wr reg_wr;
-	int ret;
+	int ret, off = 0;
 
 	while (atomic_dec_return(&ibmr->ic->i_fastreg_wrs) <= 0) {
 		atomic_inc(&ibmr->ic->i_fastreg_wrs);
 		cpu_relax();
 	}
 
-	ret = ib_map_mr_sg_zbva(frmr->mr, ibmr->sg, ibmr->sg_len, 0, PAGE_SIZE);
+	ret = ib_map_mr_sg_zbva(frmr->mr, ibmr->sg, ibmr->sg_len,
+				&off, PAGE_SIZE);
 	if (unlikely(ret != ibmr->sg_len))
 		return ret < 0 ? ret : -EINVAL;