UPSTREAM: usb: gadget: uvc: move structs to common header

The functions and structs of the configfs interface should also be used
by the uvc gadget driver. This patch prepares the stack by moving the
common structs and functions to the common header file.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

Link: https://lore.kernel.org/r/20220421211427.3400834-5-m.grzeschik@pengutronix.de


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

(cherry picked from commit e2fa7b36)
Bug: 242344221
Change-Id: I682ca939d2f6092868c75aa73ca3a98713ffca84
Signed-off-by: Avichal Rakesh <arakesh@google.com>
(cherry picked from commit 391080e7)