net: Add netdev interfaces for recording sends/comp

Add interfaces for drivers to call for recording number of packets and
bytes at send time and transmit completion.  Also, added a function to
"reset" a queue.  These will be used by Byte Queue Limits.

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>