[media] media: imx: Add CSI subdev driver

This is a media entity subdevice for the i.MX Camera
Sensor Interface module.

- Added support for negotiation of frame intervals.
- Fixed cropping rectangle negotiation at input and output pads.
- Added support for /2 downscaling, if the output pad dimension(s)
  are 1/2 the crop dimension(s) at csi_setup() time.

Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
[hans.verkuil@cisco.com: add linux/pinctrl/consumer.h include]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>