drm/amdgpu: disable VCN2.5 ib test for Arcturus sriov

currently using TMR loading VCN fw MMSCH would fail
to init after FLR, just disable ib test for temporarily
daily testing, continuing debug with mm team.

Signed-off-by: Jane Jian <Jane.Jian@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>