drm/amdgpu: drop ttm two ended allocation

amdgpu_bo_create() calls amdgpu_ttm_placement_from_domain()
before ttm_bo_init() is called.  amdgpu_ttm_placement_from_domain()
uses the ttm bo size to determine when to select top down
allocation but since the ttm bo is not initialized yet the
check is always false.  It only took affect when buffers
were validated later.  It also seemed to regress suspend
and resume on some systems possibly due to it not
taking affect in amdgpu_bo_create().

amdgpu_bo_create() and amdgpu_ttm_placement_from_domain()
need to be reworked substantially for this to be optimally
effective.  Re-enable it at that point.

Ported from radeon commit:
a239118a

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>