usb: cdns3: gadget: move wait configuration operation

After commit f4cfe5ce

 ("usb: cdns3: gadget: improve the
set_configuration handling"), the software will inform the
hardware the request has finished at cdns3_ep0_complete_setup.
The configuration set bit is only set after request has finished,
so it needs to move waiting operation after that. Meanwhile,
if it is timeout, it will show warning message and return error.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>