ice: Use more generic names for ice_ptp_tx fields

Some supported devices have per-port timestamp memory blocks while
others have shared ones within quads. Rename the struct ice_ptp_tx
fields to reflect the block entities it works with

Signed-off-by: Sergey Temerkhanov <sergey.temerkhanov@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>