drm/amd/display: Add color transfer-function tests

[WHY]
The color transfer-function calculation helpers were not covered by
the amdgpu_dm_color KUnit suite. They rely on DAL fixed-point math
and run under the KUnit UML build without native floating point.

[HOW]
Expose the five static helpers to KUnit and add direct coverage for
the legacy, 16-bit, and 32-bit input and output transfer-function
paths, including sRGB, linear, and ROM-backed variants.

Assisted-by: Copilot:GPT-5.6-Sol
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions