drm/radeon: drop ttm two ended allocation

radeon_bo_create() calls radeon_ttm_placement_from_domain()
before ttm_bo_init() is called.  radeon_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 effect when buffers
were validated later.  It also seemed to regress suspend
and resume on some systems possibly due to it not
taking effect in radeon_bo_create().

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

Noticed-by: Oded Gabbay <oded.gabbay@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org