ep0 request dequeue for function drivers

[Pratham Pratap <prathampratap@codeaurora.org>]

Hi,

Let's say a function driver queues a request on ep0 and before the 
completion handler could run composition switch/physical disconnect 
happens. This request will be in pending list since gadget_giveback is 
not done but the composite driver will free the request from 
composite_dev_cleanup. Now, once the next connect happens, another ep0 
request is queued and while handling the completion of that request, 
gadget driver might end up accessing the old/stale request leading to 
list_poison since pending list is corrupted.

To fix this, the function drivers might want to use setup_pending(mark 
it to true) flag so that when composite_dev_cleanup is run the requests 
are given back from usb_ep_dequeue; clear the setup pending flag in 
function driver when completion handler is run successfully. I can see 
this issue in almost all the function drivers.

Looking for suggestions and comments.

--Pratham