LinuxKPI: 802.11: fix locking in lkpi_ic_ampdu_rx_stop()

net80211 has inconsistent locking when calling into (*ic_ampdu_rx_stop)().
Make use of 054c5ddf587a7 and conditionally check if the caller
locked or not and if locked temporary drop the lock to avoid sleeping
on a non-sleepaable lock during the downcall into the driver.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days