LinuxKPI: 802.11: lsta txq locking cleanup

Rename the LSTA lock to LSTA_TXQ lock as that is really what it is and
put down the full set of macros. Replace the init and destroy with the
macro invocation rather than direct code.

Put locking around the txq_ready unset and check. Move the taskq_enqueue
call under lock to be sure we do not call it anymore after txq_ready
got unset.

Leave a comment related to the node reference which is passed into the
TX path on the recvif mbuf pointer.

Approved by: re (cperciva)
Fixes: 0936c648ad0ee
PR: 274382 (possibly)
Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D43909

(cherry picked from commit fa4e4257943650c0b5f58c01bb0bdfadea61dfb2)
(cherry picked from commit 763b10806cd4ebdcbd2b6753d4f50ec088dc57fb)