drm/amdgpu: add support for per VM BOs v2

Per VM BOs are handled like VM PDs and PTs. They are always valid and don't
need to be specified in the BO lists.

v2: validate PDs/PTs first

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