ath9k: fix null pointer dereference in ani monitor code

In 'ath9k_ani_reset' the 'ahp->ah_curani' will be initialized only
if 'DO_ANI(ah)' true. In 'ath9k_hw_ani_monitor' we are using
'ahp->ah_curani' unconditionally, and it will cause a NULL pointer
dereference on AR9100.

Changes-licensed-under: ISC

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Tested-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath9k/ani.c b/drivers/net/wireless/ath9k/ani.c
index 4dd0860..42197ff 100644
--- a/drivers/net/wireless/ath9k/ani.c
+++ b/drivers/net/wireless/ath9k/ani.c
@@ -551,6 +551,9 @@
 	struct ar5416AniState *aniState;
 	int32_t listenTime;
 
+	if (!DO_ANI(ah))
+		return;
+
 	aniState = ahp->ah_curani;
 	ahp->ah_stats.ast_nodestats = *stats;
 
@@ -610,9 +613,6 @@
 		aniState->cckPhyErrCount = cckPhyErrCnt;
 	}
 
-	if (!DO_ANI(ah))
-		return;
-
 	if (aniState->listenTime > 5 * ahp->ah_aniPeriod) {
 		if (aniState->ofdmPhyErrCount <= aniState->listenTime *
 		    aniState->ofdmTrigLow / 1000 &&