[PATCH] e1000: Added RX buffer enhancements

Align the prefetches to a dword to help speed them up.
Recycle skb's and early replenish.
Force memory writes to complete before fetching more descriptors.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: John Ronciak <john.ronciak@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>