gpu: ipu-v3: ipu-ic: allow to manually set resize coefficients

For tiled scaling, we want to compute the scaling coefficients
externally in such a way that the interpolation overshoots tile
boundaries and samples up to the first pixel of the next tile.
Prepare to override the resizing coefficients from the image
conversion code.

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