bonding: wrap slave state work

transfers slave->state into slave->backup (that it's going to transfer
into bitfield. Introduce wrapper inlines to do the work with it.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index a5d5d0b..494bf96 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -246,7 +246,7 @@
  */
 static inline int __port_is_enabled(struct port *port)
 {
-	return port->slave->state == BOND_STATE_ACTIVE;
+	return bond_is_active_slave(port->slave);
 }
 
 /**