gpu: ipu-v3: image-convert: Fix image downsize coefficients

The output of the IC downsizer unit in both dimensions must be <= 1024
before being passed to the IC resizer unit. This was causing corrupted
images when:

input_dim > 1024, and
input_dim / 2 < output_dim < input_dim

Some broken examples were 1920x1080 -> 1024x768 and 1920x1080 ->
1280x1080.

Fixes: 70b9b6b3 ("gpu: ipu-v3: image-convert: calculate per-tile
resize coefficients")

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