[V2,2/4] usb: gadget: configfs: Create control_config group

[Felipe Balbi <balbi@kernel.org>]

Jerry Zhang <zhangjerry@google.com> writes:

> Control_config is a group under gadget that acts
> as a normal config group, except it does not
> appear in cdev->configs.
>
> Functions that have exactly zero descriptors can
> be linked into control_config. These functions
> are bound and unbound with the rest of the gadget,
> but are never enabled. Also, functions with zero
> descriptors cannot be used in real configs.
>
> Create configfs_setup(), which will first attempt
> composite setup. If that fails, it will go through
> functions in control_config and use req_match to
> find and deliver the request to a function that can
> handle it.
>
> This allows the user to create a functionfs instance
> dedicated to handling non-standard control requests
> no matter what functions or configurations are
> currently active.
>
> Signed-off-by: Jerry Zhang <zhangjerry@google.com>

I didn't get patch 1