[PATCH] usb: gadget: fsl_udc_core: do not immediatly prime STATUS for IN xfer

[Chen Peter-B29397]

> 
> Because the fsl_udc_core driver shares one 'status_req' object for the
> complete ep0 control transfer, it is not possible to prime the final
> STATUS phase immediately after the IN transaction.  E.g. ch9getstatus()
> executed:
> 
> | req = udc->status_req;
> | ...
> | list_add_tail(&req->queue, &ep->queue);
> | if (ep0_prime_status(udc, EP_DIR_OUT))
> |       ....
> |       struct fsl_req *req = udc->status_req;
> |       list_add_tail(&req->queue, &ep->queue);
> 
> which corrupts the ep->queue list by inserting 'status_req' twice.  This
> causes a kernel oops e.g. when 'lsusb -v' is executed on the host.
> 
> Patch delays the final 'ep0_prime_status(udc, EP_DIR_OUT))' by moving it
> into the ep0 completion handler.
> 
Enrico, thanks for pointing this problem.

As "prime STATUS phase immediately after the IN transaction" is followed
USB 2.0 spec, to fix this problem, it is better to add data_req for ep0.
In fact, it is already at FSL i.mx internal code, just still not mainlined.

Peter