igc: Add 64 bit DMA access support

On relevant platforms ndo_start_xmit can handle socket buffer
fragments in high memory

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>