drm/amd/display: Initialize new backlight_level_params structure

[Why]
Initialize the new backlight_level_params structure as part of the ABC
framework, the information in this structure is needed to be passed down
to the DMCUB to identify the backlight control type, to adjust the
backlight of the panel and to perform any required conversions from PWM
to nits or vice versa.

[How]
Created initial framework of the backlight_level_params struct and
modified existing functions to include the new structure.

Reviewed-by: Harry Vanzylldejong <harry.vanzylldejong@amd.com>
Reviewed-by: Iswara Nagulendran <iswara.nagulendran@amd.com>
Reviewed-by: Anthony Koo <anthony.koo@amd.com>
Signed-off-by: Kaitlyn Tse <Kaitlyn.Tse@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>