drm/amd/display: Add Logging for Gamma Related information (2/2)

[Why]
A recent bug showed that logging would be useful in debugging
various gamma issues.

[How]
Add logging in dc.

Signed-off-by: Wyatt Wood <wyatt.wood@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>