rdma/core: Fix sparse warnings

Clean up sparse warnings in the rdma core layer.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/include/rdma/ib_addr.h b/include/rdma/ib_addr.h
index 639a449..9996539 100644
--- a/include/rdma/ib_addr.h
+++ b/include/rdma/ib_addr.h
@@ -281,7 +281,7 @@
 static inline struct net_device *rdma_vlan_dev_real_dev(const struct net_device *dev)
 {
 	return dev->priv_flags & IFF_802_1Q_VLAN ?
-		vlan_dev_real_dev(dev) : 0;
+		vlan_dev_real_dev(dev) : NULL;
 }
 
 #endif /* IB_ADDR_H */