igb: Create separate functions for generating cmd_type and olinfo

This change is meant to improve the readability of the driver by separating
out the cmd_type configuration and the olinfo configuration into their own
functions.  By doing this it is much easier to determine which ingredients
go into setting up these to portions of the descriptor.

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>
diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 7185667..1608110 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -231,7 +231,7 @@
 
 #define IGB_RING_FLAG_TX_CTX_IDX     0x00000001 /* HW requires context index */
 
-#define IGB_ADVTXD_DCMD (E1000_TXD_CMD_EOP | E1000_TXD_CMD_RS)
+#define IGB_TXD_DCMD (E1000_ADVTXD_DCMD_EOP | E1000_ADVTXD_DCMD_RS)
 
 #define IGB_RX_DESC(R, i)	    \
 	(&(((union e1000_adv_rx_desc *)((R)->desc))[i]))