mac80211: reduce duplication in tx status functions

Move redundant functionality from __ieee80211_tx_status into
ieee80211_tx_status_ext. Preparation for unifying with the 802.3 tx status
codepath.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20200908123702.88454-7-nbd@nbd.name


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