drm/amd/display: Fix pipe split prediction

[Why & How]
- Pipe split prediction previously only took into
account MPC split. We must also consider when
ODM combine is required, and when we apply ODM
combine by policy.

- Also re-work DET allocation function as it wasn't
properly splitting the DET per stream, per plane.

Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>