drm/amd/display: Add fullscreen only sharpening policy

[WHAT & HOW]
Disable sharpening if not in fullscreen if this policy is selected

Reviewed-by: Samson Tam <samson.tam@amd.com>
Signed-off-by: Relja Vojvodic <Relja.Vojvodic@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>