drm/amd: Pass luminance data to amdgpu_dm_backlight_caps

The ATIF method on some systems will provide a backlight curve. Pass
this curve into amdgpu_dm add it to the structures.

Reviewed-by: Alex Hung <alex.hung@amd.com>
Link: https://lore.kernel.org/r/20250228185145.186319-3-mario.limonciello@amd.com


Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>