drm/amdgpu: fix userq VM validation v4

drm/amdgpu: fix userq VM validation v4

That was actually complete nonsense and not validating the BOs
at all. The code just cleared all VM areas were it couldn't grab the
lock for a BO.

Try to fix this. Only compile tested at the moment.

v2: fix fence slot reservation as well as pointed out by Sunil.
    also validate PDs, PTs, per VM BOs and update PDEs
v3: grab the status_lock while working with the done list.
v4: rename functions, add some comments, fix waiting for updates to
    complete.
v4: rename amdgpu_vm_lock_done_list(), add some more comments

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>