drm/amdgpu: fix VM sync with always valid BOs v2

All users of a VM must always wait for updates with always
valid BOs to be completed.

v2: remove debugging leftovers, rename struct member

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Roger He <Hongbo.He@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>