ixgbe: Drop l2_accel_priv data pointer from ring struct

The l2 acceleration private pointer isn't needed in the ring struct. It
isn't really used anywhere other than to test and see if we are supporting
an offloaded macvlan netdev, and it is much easier to test netdev for not
being ixgbe based to verify that.

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>