drm/amd/display: Fixes for mcache programming in DML21

drm/amd/display: Fixes for mcache programming in DML21

[WHY & HOW]
- Fix indexing phantom planes for mcache programming in the wrapper
- Fix phantom mcache allocations to align with HW guidance
- Fix mcache assignment for chroma plane for multi-planar formats

Reviewed-by: Austin Zheng <Austin.Zheng@amd.com>
Signed-off-by: Dillon Varone <dillon.varone@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>