ath9k: Add tx-failed counter.

This counts any failure during getting packets into
the DMA buffers, including out-of-memory, etc.

Signed-off-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index eeea81b..5de648c 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1152,6 +1152,7 @@
 
 	if (ath_tx_start(hw, skb, &txctl) != 0) {
 		ath_dbg(common, XMIT, "TX failed\n");
+		TX_STAT_INC(txctl.txq->axq_qnum, txfailed);
 		goto exit;
 	}