staging: rtlwifi: use !x in place of NULL comparison

Challenge suggested by coccinelle.
Avoid NULL comparison, compare using boolean operator.
Signed-off-by: Payal Kshirsagar <payal.s.kshirsagar.98@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtlwifi/btcoexist/halbtcoutsrc.c

@@ -33,7 +33,7 @@ static const char *const gl_btc_wifi_freq_string[] = {
 
 static bool halbtc_is_bt_coexist_available(struct btc_coexist *btcoexist)
 {
-	if (!btcoexist->binded || NULL == btcoexist->adapter)
+	if (!btcoexist->binded || !btcoexist->adapter)
 		return false;
 
 	return true;