iwlwifi: cherry-pick fixes from upstream iwlwifi-next

Cherry-pick f973795a8d19cbf3d03807704eb7c6ff65788d5a (Fix a double free
in iwl_txq_dyn_alloc_dma), db66abeea3aefed481391ecc564fb7b7fb31d742
(synchronize with FW after multicast commands),
d5d8ee526d1401173ad1261c3b6388a4f947e0a3 (remove session protection
upon station removal), and 8e967c137df3b236d2075f9538cb888129425d1a
(avoid clearing a just saved session protection id).

Sponsored by: The FreeBSD Foundation

(cherry picked from commit 8f06a2b550c6288b48996036c325a1999780cb6a)