drm/amd/display: Fix display corruption w/ VSR enable

[Why]
Brief corruption is observed on hotplug/unplug with certain display
configurations when VSR is enabled.

[How]
Work around the issue by avoiding 2to1 ODM when stream plane_count is 0.

Reviewed-by: Dillon Varone <Dillon.Varone@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Ilya Bakoulin <Ilya.Bakoulin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>