mac80211: fix tx status for no ack cases

Before this patch, frames which where successfully transmitted without
requiring acks where accounted as lost frames.

Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
Link: https://lore.kernel.org/r/20191218142736.15843-1-markus.theil@tu-ilmenau.de


Signed-off-by: Johannes Berg <johannes.berg@intel.com>