iwlwifi: pcie: actually release queue memory in TVQM

The iwl_trans_pcie_dyn_txq_free() function only releases the frames
that may be left on the queue by calling iwl_pcie_gen2_txq_unmap(),
but doesn't actually free the DMA ring or byte-count tables for the
queue. This leads to pretty large memory leaks (at least before my
queue size improvements), in particular in monitor/sniffer mode on
channel hopping since this happens on every channel change.

This was also now more evident after the move to a DMA pool for the
byte count tables, showing messages such as

  BUG iwlwifi:bc (...): Objects remaining in iwlwifi:bc on __kmem_cache_shutdown()

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=206811.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Fixes: 6b35ff91 ("iwlwifi: pcie: introduce a000 TX queues management")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20200417100405.f5f4c4193ec1.Id5feebc9b4318041913a9c89fc1378bb5454292c@changeid

drivers/net/wireless/intel/iwlwifi/pcie/tx-gen2.c

@@ -1418,6 +1418,9 @@ void iwl_trans_pcie_dyn_txq_free(struct iwl_trans *trans, int queue)
 
 	iwl_pcie_gen2_txq_unmap(trans, queue);
 
+	iwl_pcie_gen2_txq_free_memory(trans, trans_pcie->txq[queue]);
+	trans_pcie->txq[queue] = NULL;
+
 	IWL_DEBUG_TX_QUEUES(trans, "Deactivate queue %d\n", queue);
 }