[Why]
Improved contrast in ABM 2.2 is desired

[How]
Increase the contrast factor for ABM levels 2, 3 and 4
Signed-off-by: Josip Pavic <Josip.Pavic@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>