drm/amd/display: Only use EETF when maxCL > max display

drm/amd/display: Only use EETF when maxCL > max display

[Why&How]
BT.2390 EETF is used for tone mapping/range reduction.
Say display is 0.1 - 500 nits.
The problematic case is when content is 0-400. We apply EETF because
0<0.1 so we need to reduce the range by 0.1.

In the commit, we ignore the bottom range. Most displays map 0 to min and
then have a ramp to 0.1, so sending 0.1 is actually >0.1.
Furthermode, HW that uses 3D LUT also assumes min=0.

Signed-off-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>