A simplified approach to hang detection, used in the new ixl driver, it relies on the
passes through the local timer, and the tx queue state to determine if an actual
hang has occurred. Any time a descriptor is used (packet sent), the tx queue is
flagged as busy. Then when txeof runs, it either clears the flag when all is clean,
or resets it to 1 if ANY are cleaned, if nothing is cleaned it increments the flag.

Local timer simply checks to see if busy ever reaches MAX (10, which is configurable),
and then sets it as HUNG, at that point there is one more timer cycle in which to
have any cleans, if not a watchdog reset will occur.