i40e: Quick refactor to start moving data off stack and into Tx buffer info

This patch does some quick work to pull some of the data off of the stack
and hopefully start storing it in the Tx buffer info section of the Tx
ring.  Ideally we should be moving away from having to store much of
anything on the stack and can just maintain it all in the descriptor rings.

Change-ID: I4b4715ea1920e122502482b3f9e56a9a6cb1e9fe
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>