USB: whci-hcd: handle early deletion of endpoints

If an endpoint is deleted before it's been fully added to the hardware
list, the associated qset will not be fully initialized and an oops will
occur when complete(&qset->remove_complete) is called.  This can happen
if a queued URB is cancelled.

Fix this by only removing the qset from the hardware list if the
cancelled URB had qTDs.

Signed-off-by: David Vrabel <david.vrabel@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>