bonding: convert bond_has_slaves() to use the neighbour list

The same way as it was used for its own slave_list.

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bonding.h

@@ -72,7 +72,7 @@
 	res; })
 
 /* slave list primitives */
-#define bond_has_slaves(bond) !list_empty(&(bond)->slave_list)
+#define bond_has_slaves(bond) !list_empty(&(bond)->dev->adj_list.lower)
 
 #define bond_to_slave(ptr) list_entry(ptr, struct slave, list)