drm/amdgpu: fix ftrace event amdgpu_bo_move always move on same heap

Issue: during evict or validate happened on amdgpu_bo, the 'from' and
'to' is always same in ftrace event of amdgpu_bo_move

where calling the 'trace_amdgpu_bo_move', the comment says move_notify
is called before move happens, but actually it is called after move
happens, here the new_mem is same as bo->resource

Fix: move trace_amdgpu_bo_move from move_notify to amdgpu_bo_move

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