usb/isp1760: Fix bug preventing the unlinking of control urbs

Both control and bulk transfers use isp1760 slots of type ATL, but the
driver unlink code for ATL slots only acts on urbs describing a bulk
transfer, letting the code for INT slots take care of the unlink instead,
which often ended up removing the interrupt transfer for root hub events
instead. That's not good, and gets fixed by this patch.

Signed-off-by: Arvid Brodin <arvid.brodin@enea.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>