usb: cdns3: gadget: Remove unneeded variable ret

Remove unneeded variable ret used to store return value,just return 0.

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Acked-by: Roger Quadros <rogerq@ti.com>
Link: https://lore.kernel.org/r/1576826378-4387-1-git-send-email-vulab@iscas.ac.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>