e1000e: 82579 performance improvements

e1000e: 82579 performance improvements

The initial support for 82579 was tuned poorly for performance.  Adjust the
packet buffer allocation appropriately for both standard and jumbo frames;
and for jumbo frames increase the receive descriptor pre-fetch, disable
adaptive interrupt moderation and set the DMA latency tolerance.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>