usb: gadget: composite: reset delayed_status on reset_config

The delayed_status value is used to keep track of status response
packets on ep0. It needs to be reset or the set_config function would
still delay the answer, if the usb device got unplugged while waiting
for setup_continue to be called.

Cc: stable@vger.kernel.org
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>