drm/amd/display: Allow Z8 when stutter threshold is not met

drm/amd/display: Allow Z8 when stutter threshold is not met

[Why&How]
Some panels don't meet the stutter threshold (4k etc), this leads to
power regressions. Allow z8 for panels that don't meet the threshold
but support PSR/replay

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>