e1000e: start network tx queue only when link is up

Driver does not want to keep packets in Tx queue when link is lost.
But present code only reset NIC to flush them, but does not prevent
queuing new packets. Moreover reset sequence itself could generate
new packets via netconsole and NIC falls into endless reset loop.

This patch wakes Tx queue only when NIC is ready to send packets.

This is proper fix for problem addressed by commit 0f9e980b
("e1000e: fix cyclic resets at link up with active tx").

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Tested-by: Joseph Yasi <joe.yasi@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Tested-by: Oleksandr Natalenko <oleksandr@redhat.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>