usb: dwc3: Delete the request from pending list in case of ep queue failure

While queuing the request to an ep we add the request to pending list
and after adding, if usb disconnect occurs then ep queue failure is
seen and the request which is added to pending list will be added back
to the pool in function driver without deleting the request from pending
list. As a part of disconnect we call gadget_giveback_request which will
give back requests from the pending list to the function driver and the
same request will be added to the pool again.

To prevent the same request to be added to pool twice delete the request
from pending list when ep_queue fails.

Change-Id: I0f679266257e969f75b14e06add2e3f4bb894dfb
Signed-off-by: Rohith Kollalsi <rkollals@codeaurora.org>