e1000e: Disable TSO for buffer overrun workaround

Commit b10effb9 ("e1000e: fix buffer overrun while the I219 is
processing DMA transactions") imposes roughly 30% performance penalty.

The commit log states that "Disabling TSO eliminates performance loss
for TCP traffic without a noticeable impact on CPU performance", so
let's disable TSO by default to regain the loss.

CC: stable <stable@vger.kernel.org>
Fixes: b10effb9 ("e1000e: fix buffer overrun while the I219 is processing DMA transactions")
BugLink: https://bugs.launchpad.net/bugs/1802691


Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>