Fix video playback on Windows 10

Doing a blocking read (even with count=0) when handling a cancel request
from the host ends up blocking both the read in the request handler as
well as a write in the thread that's being cancelled, blocking both threads
indefinitely.
Removing the read appears to fix the problem.
Fixes #108

src/usb_gadget.c

@@ -498,8 +498,6 @@ static void handle_setup_request(usb_gadget * ctx, struct usb_ctrlrequest* setup
 		case MTP_REQ_CANCEL:
 			PRINT_DEBUG("MTP_REQ_CANCEL !");
 
-			status = read (ctx->usb_device, &status, 0);
-
 			mtp_context->cancel_req = 1;
 
 			cnt = 0;