gpu: ipu-v3: image-convert: allow three rows or columns

If width or height are in the [2049, 3072] range, allow to
use just three tiles in this dimension, instead of four.

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