Revert "drm/amdgpu: move PD/PT bos on LRU again"

This reverts commit 31625ccae4464b61ec8cdb9740df848bbc857a5b.

It triggered various badness on my development machine when running the
piglit gpu profile with radeonsi on Bonaire, looks like memory
corruption due to insufficiently protected list manipulations.

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>