ixgbevf: Remove the ring adapter pointer value

It is unused - remove it.
Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbevf/ixgbevf.h

@@ -58,7 +58,6 @@ struct ixgbevf_ring {
 	struct ixgbevf_ring *next;
 	struct net_device *netdev;
 	struct device *dev;
-	struct ixgbevf_adapter *adapter;  /* backlink */
 	void *desc;			/* descriptor ring memory */
 	dma_addr_t dma;			/* phys. address of descriptor ring */
 	unsigned int size;		/* length in bytes */