igb: consolidate creation of Tx buffer info and data descriptor

This change will combine the writes of tx_buffer_info and the Tx data
descriptors into a single function. The advantage of this is that we can
avoid needless memory reads from the buffer info struct and speed things up
by keeping the accesses to the local registers.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown  <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb.h

@@ -135,7 +135,6 @@ struct vf_data_storage {
 #define IGB_TX_FLAGS_TSO		0x00000004
 #define IGB_TX_FLAGS_IPV4		0x00000008
 #define IGB_TX_FLAGS_TSTAMP		0x00000010
-#define IGB_TX_FLAGS_MAPPED_AS_PAGE	0x00000020
 #define IGB_TX_FLAGS_VLAN_MASK		0xffff0000
 #define IGB_TX_FLAGS_VLAN_SHIFT	16
 
@@ -144,13 +143,12 @@ struct vf_data_storage {
 struct igb_tx_buffer {
 	union e1000_adv_tx_desc *next_to_watch;
 	unsigned long time_stamp;
-	dma_addr_t dma;
-	u32 length;
-	u32 tx_flags;
 	struct sk_buff *skb;
 	unsigned int bytecount;
 	u16 gso_segs;
-	u8 mapped_as_page;
+	dma_addr_t dma;
+	u32 length;
+	u32 tx_flags;
 };
 
 struct igb_rx_buffer {