Revert "[PATCH] e1000: disable TSO on the 82544 with slab debugging"

This reverts commit 72f3ab7462f4e153d1e8ac78e379716ad71d6923, which was
superceded by commit 683a2aa339f607c8a422835161ceab68b2a5a18a
("e1000: Do not truncate TSO TCP header with 82544 workaround"), which
fixed the real problem.

Signed-off-by: Jeff Garzik <jeff@garzik.org>