ixgbe: remove redundant if clause from PTP work

ptp_tx_skb is always set before work is scheduled,
work is cancelled before ptp_tx_skb is set to NULL.
PTP work cannot ever see ptp_tx_skb set to NULL.
Signed-off-by: NJakub Kicinski <kubakici@wp.pl>
Tested-by: NPhil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c

@@ -512,10 +512,6 @@ static void ixgbe_ptp_tx_hwtstamp_work(struct work_struct *work)
 					      IXGBE_PTP_TX_TIMEOUT);
 	u32 tsynctxctl;
 
-	/* we have to have a valid skb */
-	if (!adapter->ptp_tx_skb)
-		return;
-
 	if (timeout) {
 		dev_kfree_skb_any(adapter->ptp_tx_skb);
 		adapter->ptp_tx_skb = NULL;