ath9k: Fix interface accounting

Currently, the interface count is maintained globally,
but this causes problems in RX filter calculation.
Make the interface count a per-channel-context variable
to fix this.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 4f3da18..46a1d2e 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -350,6 +350,7 @@
 	bool assigned;
 	bool switch_after_beacon;
 
+	short nvifs;
 	unsigned int rxfilter;
 };
 
@@ -963,7 +964,6 @@
 	bool ps_enabled;
 	bool ps_idle;
 	short nbcnvifs;
-	short nvifs;
 	unsigned long ps_usecount;
 
 	struct ath_rx rx;