mac80211: add support for per-chain signal strength reporting

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
[fix unit documentation]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index adc3004..41c28b9 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -344,6 +344,11 @@
 	int last_signal;
 	struct ewma avg_signal;
 	int last_ack_signal;
+
+	u8 chains;
+	s8 chain_signal_last[IEEE80211_MAX_CHAINS];
+	struct ewma chain_signal_avg[IEEE80211_MAX_CHAINS];
+
 	/* Plus 1 for non-QoS frames */
 	__le16 last_seq_ctrl[IEEE80211_NUM_TIDS + 1];