media: ipu6: isys: Set minimum height to 1

For image data generally 2 seems like a minimum height that surely won't
cause any issues, but some sensors have metadata the height of which is
just one line. Set the minimum height to 1.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>