IB/{core,hw}: Add constant for node_desc

Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/drivers/infiniband/hw/mthca/mthca_mad.c b/drivers/infiniband/hw/mthca/mthca_mad.c
index 7c3f2fb..9139405 100644
--- a/drivers/infiniband/hw/mthca/mthca_mad.c
+++ b/drivers/infiniband/hw/mthca/mthca_mad.c
@@ -153,7 +153,8 @@
 	    mad->mad_hdr.method == IB_MGMT_METHOD_GET_RESP &&
 	    mad->mad_hdr.attr_id == IB_SMP_ATTR_NODE_DESC) {
 		mutex_lock(&to_mdev(dev)->cap_mask_mutex);
-		memcpy(((struct ib_smp *) mad)->data, dev->node_desc, 64);
+		memcpy(((struct ib_smp *) mad)->data, dev->node_desc,
+		       IB_DEVICE_NODE_DESC_MAX);
 		mutex_unlock(&to_mdev(dev)->cap_mask_mutex);
 	}
 }