igb: place a pointer to the netdev struct in the ring itself

This change adds a pointer to the netdev to the ring itself.  The idea being
at some point in the future it will be possible to support multiple netdevs
from a single adapter struct.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb.h

@@ -175,9 +175,10 @@ struct igb_q_vector {
 
 struct igb_ring {
 	struct igb_q_vector *q_vector; /* backlink to q_vector */
-	void *desc;                    /* descriptor ring memory */
+	struct net_device *netdev;     /* back pointer to net_device */
 	struct pci_dev *pdev;          /* pci device for dma mapping */
 	dma_addr_t dma;                /* phys address of the ring */
+	void *desc;                    /* descriptor ring memory */
 	unsigned int size;             /* length of desc. ring in bytes */
 	unsigned int count;            /* number of desc. in the ring */
 	u16 next_to_use;