usb: Handle GET_REQUEST (Device) as required by USB specification.

Fixes greaseweazle issue 282

src/usb/core.c

@@ -35,6 +35,13 @@ static bool_t handle_control_request(void)
         WARN("Ctl OUT too long: %u>%u\n", req->wLength, sizeof(ep0.data));
         handled = FALSE;
 
+    } else if ((req->bmRequestType == 0x80)
+               && (req->bRequest == GET_STATUS)) {
+
+        /* GET_STATUS (Device) */
+        ep0.data_len = 2;
+        memset(ep0.data, 0, ep0.data_len);
+
     } else if ((req->bmRequestType == 0x80)
                && (req->bRequest == GET_DESCRIPTOR)) {