drm/amdgpu: fix wrong release of vmid owner

The release of the vmid owner was not handled
correctly.  We need to take the lock and walk
the lru list.

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>