drm/amd/display: Multi display cause system lag on mode change

[Why]
DCValidator is created/destroyed repeatedly for cofunctional validation
which causes a lot of memory thrashing, particularly when Driver Verifer
is enabled.

[How]
Implement a basic caching algorithm that will cache DCValidator with a
matching topology.  When a match is found, the DCValidator can be
reused.  If there is no match, a new one will be created and inserted
into the cache if there is space or an unreference entry can be evicted.

Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>