mac80211: remove TX latency measurement code

Revert commit ad38bfc916 ("mac80211: Tx frame latency statistics")
(along with some follow-up fixes).

This code turned out not to be as useful in the current form as we
thought, and we've internally hacked it up more, but that's not
very suitable for upstream (for now), and we might just do that
with tracing instead.

Therefore, for now at least, remove this code. We might also need
to use the skb->tstamp field for the TCP performance issue, which
is more important than the debugging.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -1030,24 +1030,6 @@ struct tpt_led_trigger {
 };
 #endif
 
-/*
- * struct ieee80211_tx_latency_bin_ranges - Tx latency statistics bins ranges
- *
- * Measuring Tx latency statistics. Counts how many Tx frames transmitted in a
- * certain latency range (in Milliseconds). Each station that uses these
- * ranges will have bins to count the amount of frames received in that range.
- * The user can configure the ranges via debugfs.
- * If ranges is NULL then Tx latency statistics bins are disabled for all
- * stations.
- *
- * @n_ranges: number of ranges that are taken in account
- * @ranges: the ranges that the user requested or NULL if disabled.
- */
-struct ieee80211_tx_latency_bin_ranges {
-	int n_ranges;
-	u32 ranges[];
-};
-
 /**
  * mac80211 scan flags - currently active scan mode
  *
@@ -1199,12 +1181,6 @@ struct ieee80211_local {
 	struct timer_list sta_cleanup;
 	int sta_generation;
 
-	/*
-	 * Tx latency statistics parameters for all stations.
-	 * Can enable via debugfs (NULL when disabled).
-	 */
-	struct ieee80211_tx_latency_bin_ranges __rcu *tx_latency;
-
 	struct sk_buff_head pending[IEEE80211_MAX_QUEUES];
 	struct tasklet_struct tx_pending_tasklet;