drm/amd/display: new ABM config 2

[Why & How]
Add configuration 2 for ABM 2.3/2.4 to suit customer preferences, which
is to lower the brightness curves in 80%-100% range compared to the
existing default config 0.

Reviewed-by: Josip Pavic <Josip.Pavic@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Camille Cho <Camille.Cho@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>