MLK-18809: drm: imx: dcss: revert the max upscale ratio to 1:8

MLK-18809: drm: imx: dcss: revert the max upscale ratio to 1:8

The DCSS RM states that the maximum upscale ratio is 1:8. However, DCSS
HW team suggested some time back that upscale ratios of 1:16 could be
achieved with DCSS scaler, though these ratios were not validated.

Unfortunately there are corner cases, when the upscale ratio nears
1:16, that fail. At the recommendation of DCSS designers, we revert the
maximum ratio to 1:8 until further notice.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@nxp.com>
(cherry picked from commit bafb5a9481c289951872923d4bbbbcf24a8910b5)