drm/amdgpu: group BOs by log2 of the size on the LRU v2

This allows us to have small BOs on the LRU before big ones.

v2: fix of by one and list corruption bug

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