drm/amd/display: fix unnecessary pipe split playing NV12 1080p MPO video

drm/amd/display: fix unnecessary pipe split playing NV12 1080p MPO video

[Why]
When playing NV12 1080p MPO video, it is pipe splitting so
we see two pipes in fullscreen and four pipes in windowed
mode. Pipe split is happening because we are setting
MaximumMPCCombine = 1

[How]
Algorithm for MaximumMPCCombine has extra conditions we do
not need.  Use DCN31 algorithm instead

Signed-off-by: Samson Tam <Samson.Tam@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>