staging: wilc1000: make function wilc_get_stats_async static

Makes local function wilc_get_stats_async() static

Cleans up sparse warning:
symbol 'wilc_get_stats_async' was not declared. Should it be static?
Signed-off-by: Marko Stankovic <dartnorris@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wilc1000/host_interface.c

@@ -1992,7 +1992,7 @@ int wilc_get_rssi(struct wilc_vif *vif, s8 *rssi_level)
 	return result;
 }
 
-int wilc_get_stats_async(struct wilc_vif *vif, struct rf_info *stats)
+static int wilc_get_stats_async(struct wilc_vif *vif, struct rf_info *stats)
 {
 	int result;
 	struct host_if_msg *msg;