igb/igbvf: cleanup exception handling in tx_map_adv

After removing the skb_dma_map/unmap calls the exception handling in
igb_tx_map_adv is not correct.  The issue is that the count value was not
being correctly handled so as a result we were not rewinding the ring as
back as we should have been.

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_main.c

@@ -3584,6 +3584,7 @@ static inline int igb_tx_map_adv(struct igb_ring *tx_ring, struct sk_buff *skb,
 	for (f = 0; f < skb_shinfo(skb)->nr_frags; f++) {
 		struct skb_frag_struct *frag;
 
+		count++;
 		i++;
 		if (i == tx_ring->count)
 			i = 0;
@@ -3605,7 +3606,6 @@ static inline int igb_tx_map_adv(struct igb_ring *tx_ring, struct sk_buff *skb,
 		if (pci_dma_mapping_error(pdev, buffer_info->dma))
 			goto dma_error;
 
-		count++;
 	}
 
 	tx_ring->buffer_info[i].skb = skb;

drivers/net/igbvf/netdev.c

@@ -2126,6 +2126,7 @@ static inline int igbvf_tx_map_adv(struct igbvf_adapter *adapter,
 	for (f = 0; f < skb_shinfo(skb)->nr_frags; f++) {
 		struct skb_frag_struct *frag;
 
+		count++;
 		i++;
 		if (i == tx_ring->count)
 			i = 0;
@@ -2146,7 +2147,6 @@ static inline int igbvf_tx_map_adv(struct igbvf_adapter *adapter,
 						PCI_DMA_TODEVICE);
 		if (pci_dma_mapping_error(pdev, buffer_info->dma))
 			goto dma_error;
-		count++;
 	}
 
 	tx_ring->buffer_info[i].skb = skb;