drm/amdgpu: only move VM BOs in the LRU during validation v2

This should save us a bunch of command submission overhead.

v2: move the LRU move to the right place to avoid the move for the root BO
    and handle the shadow BOs as well. This turned out to be a bug fix because
    the move needs to happen before the kmap.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>