drm/amd/display: Test MST topology start

[WHAT]
Add a KUnit test to cover dm_helpers_dp_mst_start_top_mgr() its
success path.

[HOW]
Mark the topology manager as already in MST mode, so
drm_dp_mst_topology_mgr_set_mst() returns success without touching the
AUX channel or queueing the link probe work, and the helper reports
that MST was started.

Assisted-by: Copilot:Claude-Opus-5
Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions