Since a transmit can take several control blocks, the old code waited
until the last control block was marked as done. This code processes
the return values incrementally. This makes slots in the tx ring available
and less chance of getting stuck.
Signed-off-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>