gpu: ipu-v3: image-convert: add some ASCII art to the exposition

Visualize the scaling and rotation pipeline with some ASCII art
diagrams. Remove the FIXME comment about missing seam prevention.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Steve Longerbeam <slongerbeam@gmail.com>