net/smc: fix direct access to ib_gid_addr->ndev in smc_ib_determine_gid()

Sparse complaints 3 times about:
net/smc/smc_ib.c:203:52: warning: incorrect type in argument 1 (different address spaces)
net/smc/smc_ib.c:203:52:    expected struct net_device const *dev
net/smc/smc_ib.c:203:52:    got struct net_device [noderef] __rcu *const ndev

Fix that by using the existing and validated ndev variable instead of
accessing attr->ndev directly.

Fixes: 5102eca9 ("net/smc: Use rdma_read_gid_l2_fields to L2 fields")
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/smc/smc_ib.c

@@ -198,9 +198,9 @@ int smc_ib_determine_gid(struct smc_ib_device *smcibdev, u8 ibport,
 		rcu_read_lock();
 		ndev = rdma_read_gid_attr_ndev_rcu(attr);
 		if (!IS_ERR(ndev) &&
-		    ((!vlan_id && !is_vlan_dev(attr->ndev)) ||
-		     (vlan_id && is_vlan_dev(attr->ndev) &&
-		      vlan_dev_vlan_id(attr->ndev) == vlan_id)) &&
+		    ((!vlan_id && !is_vlan_dev(ndev)) ||
+		     (vlan_id && is_vlan_dev(ndev) &&
+		      vlan_dev_vlan_id(ndev) == vlan_id)) &&
 		    attr->gid_type == IB_GID_TYPE_ROCE) {
 			rcu_read_unlock();
 			if (gid)