[PATCH] e1000: Fix Desc. Rings and Jumbo Frames

This patch contains two fixes.  The first fix is to the tx and rx descriptor rings clean up process.  The second fix is to jumbo frames, which cleans up the code logic and removes most of the fifo related limitations on jumbo frames.  This is because the driver code now supports splitting a packet across multiple descriptors.

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