ath9k: Reintroduce modparam to enable btcoex

It is not ideal to enable btcoex based on subsys id as it is
not unique, they are so random. It is also a pain keeping
all of them in a table to enable btcoex for a particular
hw. Going back to the old idea.

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index ce9e59f..883f6cc 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -1925,8 +1925,7 @@
 	pCap->num_antcfg_2ghz =
 		ah->eep_ops->get_num_ant_config(ah, ATH9K_HAL_FREQ_BAND_2GHZ);
 
-	if (AR_SREV_9280_20_OR_LATER(ah) &&
-	    ath9k_hw_btcoex_supported(ah)) {
+	if (AR_SREV_9280_20_OR_LATER(ah) && common->btcoex_enabled) {
 		btcoex_hw->btactive_gpio = ATH_BTACTIVE_GPIO;
 		btcoex_hw->wlanactive_gpio = ATH_WLANACTIVE_GPIO;