drm/amdgpu/vcn2.5: fix a bug for the 2nd vcn instance (v2)

Fix a bug for the 2nd vcn instance at start and stop.

v2: squash in unused label removal.

Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>