atl1: disable TSO by default

The atl1 driver is causing stalled connections and file corruption
whenever TSO is enabled.  Two examples are here:

http://lkml.org/lkml/2008/7/15/325
http://lkml.org/lkml/2008/8/18/543



Disable TSO by default until we can determine the source of the
problem.

Signed-off-by: Jay Cliburn <jacliburn@bellsouth.net>
cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>