sandbox: usb: Allow up to 4 emulated devices on a hub

To support more advanced testing, support 4 devices instead of 2.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/usb/emul/sandbox_hub.c b/drivers/usb/emul/sandbox_hub.c
index baf8bdc..624fbde 100644
--- a/drivers/usb/emul/sandbox_hub.c
+++ b/drivers/usb/emul/sandbox_hub.c
@@ -13,7 +13,7 @@
 DECLARE_GLOBAL_DATA_PTR;
 
 /* We only support up to 8 */
-#define SANDBOX_NUM_PORTS	2
+#define SANDBOX_NUM_PORTS	4
 
 struct sandbox_hub_platdata {
 	struct usb_dev_platdata plat;