mlxsw: Add mlxsw_txhdr_info structure

mlxsw: Add mlxsw_txhdr_info structure

mlxsw_tx_info structure is used to store information that is needed to
process Tx completions when Tx time stamps are requested. A next patch
will move Tx header handling from spectrum.c to pci.c. For that, some
additional fields which are related to Tx should be passed to pci driver.

As preparation, create an extended structure, called mlxsw_txhdr_info,
and store mlxsw_tx_info inside. The new fields should not be added to
mlxsw_tx_info structure as it is stored in the SKB control block which is
of limited size.

The next patch will extend the new structure with some fields which are
needed in order to construct Tx header.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://patch.msgid.link/93aed1961f046f79f46869bab37a3faa5027751d.1737044384.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>