usb: gadget: uvc: Copy XU descriptors during .bind()

usb: gadget: uvc: Copy XU descriptors during .bind()

Now that extension unit support is available through configfs we need
to copy the descriptors for the XUs during uvc_function_bind() so that
they're exposed to the usb subsystem.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230206161802.892954-5-dan.scally@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>