ice/ptp: fix the PTP worker retrying indefinitely if the link went down

When the link goes down the ice_ptp_tx_tstamp() may loop re-trying to
process the packets till the 2 seconds timeout finally drops them.
In such a case it makes sense to just drop them right away.

Signed-off-by: Daniel Vacek <neelx@redhat.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>