The first parameter of list_cut_position() must point to an initialized
list.

Noticed thanks to KASAN pointing out something's fishy here.

Fixes: "drm/ttm: add bulk move function on LRU"
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>