drm/amd/display: Add params of set_abm_event for VB Scaling

[Why]
Add parameters for set_abm_event to enable varibright scaling.
VariBright Scaling is a feature to refer to system states like

1. Power mode
2. Battery Life percent
3. FullScreen video
4. Backlight slider

to adjust variBright strength to get low power or user experience.

[How]
Add parameters of set_abm_event for VB Scaling

Reviewed-by: Jun Lei <jun.lei@amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Chun-LiangChang <chuchang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>