* Create ieee80211_free_mbuf() which frees a list of mbufs.
* Use it in the fragment transmit path and ath / uath transmit paths.
* Call it in xmit_pkt() if the transmission fails; otherwise fragments
may be leaked.
This should be a big no-op.
Submitted by: <s3erios@gmail.com>
Differential Revision: https://reviews.freebsd.org/D3769