drm/amd/display: Add minimum Z8 residency debug option

[Why]
Allows finer control and tuning for debug and profiling.

[How]
Add the debug option into DC. The default remains the same as before
for now.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>