i40e/i40evf: reduce context descriptors

We don't need context descriptors for every packet, only tso
or timesync.  This fixes a bug in the driver where it would
always add a context even if all the passed in values
to the context descriptor function were 0/default values.

Change-ID: I0101d2b893380707b5c2de61aab3e16d4310e9a1
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1951,7 +1951,8 @@ static void i40e_create_tx_ctx(struct i40e_ring *tx_ring,
 	struct i40e_tx_context_desc *context_desc;
 	int i = tx_ring->next_to_use;
 
-	if (!cd_type_cmd_tso_mss && !cd_tunneling && !cd_l2tag2)
+	if ((cd_type_cmd_tso_mss == I40E_TX_DESC_DTYPE_CONTEXT) &&
+	    !cd_tunneling && !cd_l2tag2)
 		return;
 
 	/* grab the next descriptor */

drivers/net/ethernet/intel/i40evf/i40e_txrx.c

@@ -1286,7 +1286,8 @@ static void i40e_create_tx_ctx(struct i40e_ring *tx_ring,
 	struct i40e_tx_context_desc *context_desc;
 	int i = tx_ring->next_to_use;
 
-	if (!cd_type_cmd_tso_mss && !cd_tunneling && !cd_l2tag2)
+	if ((cd_type_cmd_tso_mss == I40E_TX_DESC_DTYPE_CONTEXT) &&
+	    !cd_tunneling && !cd_l2tag2)
 		return;
 
 	/* grab the next descriptor */