bonding: remove useless updating of slave->dev->last_rx

Now that all the logic is handled via last_arp_rx, we don't need to use
last_rx.

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 430c51a..891432a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1312,13 +1312,7 @@
 /*
  * Cache lines mostly used on receive path (including eth_type_trans())
  */
-	unsigned long		last_rx;	/* Time of last Rx
-						 * This should not be set in
-						 * drivers, unless really needed,
-						 * because network stack (bonding)
-						 * use it if/when necessary, to
-						 * avoid dirtying this cache line.
-						 */
+	unsigned long		last_rx;	/* Time of last Rx */
 
 	/* Interface address info used in eth_type_trans() */
 	unsigned char		*dev_addr;	/* hw address, (before bcast