ixgbe: Drop real_adapter from l2 fwd acceleration structure

This patch drops the real_adapter member from the fwd_adapter structure.
The general idea behind the change is that the real_adapter is carrying
unnecessary data since we could always just grab the adapter structure
from netdev_priv(macvlan->lowerdev) if we really needed to get at it.

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>