igc: Remove timeout check from ptp_tx work

The Tx timestamp timeout is already checked by the watchdog_task
which runs periodically. In addition to that, from the ptp_tx work
perspective, if __IGC_PTP_TX_IN_PROGRESS flag is set we always want
handle the timestamp stored in hardware and update the skb. So remove
the timeout check in igc_ptp_tx_work() function.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>