usb: cdnsp: Fixes error: uninitialized symbol 'len'

usb: cdnsp: Fixes error: uninitialized symbol 'len'

The patch 5bc38d33a5a1: "usb: cdnsp: Fixes issue with redundant
Status Stage" leads to the following Smatch static checker warning:

  drivers/usb/cdns3/cdnsp-ep0.c:470 cdnsp_setup_analyze()
  error: uninitialized symbol 'len'.

cc: <stable@vger.kernel.org>
Fixes: 5bc38d33a5a1 ("usb: cdnsp: Fixes issue with redundant Status Stage")
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Link: https://lore.kernel.org/r/20230331090600.454674-1-pawell@cadence.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>