drm/ttm, drm/xe: Modify the struct ttm_bo_lru_walk_cursor initialization

drm/ttm, drm/xe: Modify the struct ttm_bo_lru_walk_cursor initialization

Instead of the struct ttm_operation_ctx, Pass a struct ttm_lru_walk_arg
to enable us to easily extend the walk functionality, and to
implement ttm_lru_walk_for_evict() using the guarded LRU iteration.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20250623155313.4901-3-thomas.hellstrom@linux.intel.com