rtlwifi: Add check for get_btc_status callback

Drivers that do not use the get_btc_status() callback may not define a
dummy routine. The caller needs to check before making the call.
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Murilo Opsfelder Araujo <mopsfelder@gmail.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Thadeu Cascardo <cascardo@cascardo.eti.br>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/pci.c

@@ -1796,7 +1796,8 @@ static int rtl_pci_start(struct ieee80211_hw *hw)
 	rtl_pci_reset_trx_ring(hw);
 
 	rtlpci->driver_is_goingto_unload = false;
-	if (rtlpriv->cfg->ops->get_btc_status()) {
+	if (rtlpriv->cfg->ops->get_btc_status &&
+	    rtlpriv->cfg->ops->get_btc_status()) {
 		rtlpriv->btcoexist.btc_ops->btc_init_variables(rtlpriv);
 		rtlpriv->btcoexist.btc_ops->btc_init_hal_vars(rtlpriv);
 	}