usb: gadget: uvc: configfs: Add section header comments

The UVC configfs implementation is large and difficult to navigate. Add
a bit more air to the code to make it easier to read.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Git-commit: f7d8109e
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>