e1000: Express TSO restart policy without OACTIVE

[kbowling]

Summary

After a link-speed change updates TSO capabilities, request a restart
when iflib is running or the interface is administratively up.  Leave
an administratively-down, stopped interface to apply the change at its
next initialization.

Do not infer initialization from IFF_DRV_OACTIVE, which also remains
set after stop and failed initialization.  Use iflib_is_running() for
software admission and IFF_UP for intent; iflib retains responsibility
for quiescing any partially initialized queues before restarting.

This also permits a restart request for an administratively-up
interface before its first initialization attempt.  No PHY, offload
eligibility or hardware-reset sequence is changed.