drm/amdgpu: allow direct submission in the VM backends v2

This allows us to update page tables directly while in a page fault.

v2: use direct/delayed entities and still wait for moves

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>