bootstd: usb: Avoid initing USB twice

This causes crashes on some boards, e.g. rockpro64. In any case, we
should not do it.

Check the usb_started flag to avoid this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Tom Rini <trini@konsulko.com>

drivers/usb/host/usb_bootdev.c

@@ -22,6 +22,9 @@ static int usb_bootdev_bind(struct udevice *dev)
 
 static int usb_bootdev_hunt(struct bootdev_hunter *info, bool show)
 {
+	if (usb_started)
+		return 0;
+
 	return usb_init();
 }