idpf: cleanup remaining SKBs in PTP flows

idpf: cleanup remaining SKBs in PTP flows

When the driver requests Tx timestamp value, one of the first steps is
to clone SKB using skb_get. It increases the reference counter for that
SKB to prevent unexpected freeing by another component.
However, there may be a case where the index is requested, SKB is
assigned and never consumed by PTP flows - for example due to reset during
running PTP apps.

Add a check in release timestamping function to verify if the SKB
assigned to Tx timestamp latch was freed, and release remaining SKBs.

Fixes: 4901e83a94ef ("idpf: add Tx timestamp capabilities negotiation")
Signed-off-by: Milena Olech <milena.olech@intel.com>
Signed-off-by: Anton Nadezhdin <anton.nadezhdin@intel.com>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20251009-jk-iwl-net-2025-10-01-v3-1-ef32a425b92a@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>