Based on work by Pravin Shelar.

Update appropriate stats when packet transmission isn't possible.
Signed-off-by: NJonas Bonn <jonas@norrbonn.se>
Acked-by: NHarald Welte <laforge@gnumonks.org>
Acked-by: NPravin B Shelar <pshelar@ovn.org>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>