media: bcm2835-unicam: Add support for CCP2/CSI2 camera interface

Add a driver for the Unicam camera receiver block on BCM283x processors.
It is represented as two video device nodes: unicam-image and
unicam-embedded which are connected to an internal subdev (named
unicam-subdev) in order to manage streams routing.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Co-developed-by: Naushir Patuck <naush@raspberrypi.com>
Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Co-developed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Co-developed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[Sakari Ailus: Squash fixes by Laurent.]
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>