usb: dwc3: Don't add the request to pending list in case of endxfer

Commit f6967121 ("usb: dwc3: Delete the request from pending
list in case of ep queue failure") deletes request from pending
or started list if ep queue failure is observed. However, this
approach is correct only if request is still in pending list and
endxfer is issued, but if request is moved to started list and any
failure occurs we delete the request in kick transfer, in this case
we are deleting the same request again in ep queue.

Inorder to avoid deleting the same request twice, don't add the
request to pending list if DWC3_EP_END_TRANSFER_PENDING flag is set
at the start of ep queue and return -ESHUTDOWN.

Change-Id: I56be446219ac3dcdd28a62a744189838af634822
Signed-off-by: Rohith Kollalsi <rkollals@codeaurora.org>