ath9k: Add a HW capability for WLAN/BT RX diversity

Make use of this capability to restrict the usage of the
debugfs file and modparam using which this feature can
be enabled.

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 74009f1..18898ab 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -634,10 +634,11 @@
 /* Main driver core */
 /********************/
 
-#define ATH9K_PCI_CUS198 0x0001
-#define ATH9K_PCI_CUS230 0x0002
-#define ATH9K_PCI_CUS217 0x0004
-#define ATH9K_PCI_WOW    0x0008
+#define ATH9K_PCI_CUS198     0x0001
+#define ATH9K_PCI_CUS230     0x0002
+#define ATH9K_PCI_CUS217     0x0004
+#define ATH9K_PCI_WOW        0x0008
+#define ATH9K_PCI_BT_ANT_DIV 0x0010
 
 /*
  * Default cache line size, in bytes.