atl1c: Fix set-but-unused variable.

The variable 'extra_size' is set but unused in
atl1c_configure_tx().  Just kill it off.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/atl1c/atl1c_main.c

@@ -1095,10 +1095,8 @@ static void atl1c_configure_tx(struct atl1c_adapter *adapter)
 	u32 max_pay_load;
 	u16 tx_offload_thresh;
 	u32 txq_ctrl_data;
-	u32 extra_size = 0;     /* Jumbo frame threshold in QWORD unit */
 	u32 max_pay_load_data;
 
-	extra_size = ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN;
 	tx_offload_thresh = MAX_TX_OFFLOAD_THRESH;
 	AT_WRITE_REG(hw, REG_TX_TSO_OFFLOAD_THRESH,
 		(tx_offload_thresh >> 3) & TX_TSO_OFFLOAD_THRESH_MASK);