usb: dwc2: gadget: remove incorrect file reference

The file and folder movements resulted in the incorrect reference.
So for better code maintainability, let's remove it.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>