lib/list_sort: fix kerneldoc build error

Commit 043b3f7b ("lib/list_sort: simplify and remove
MAX_LIST_LENGTH_BITS") added some useful kerneldoc info, but also broke the
docs build:

  ./lib/list_sort.c:128: WARNING: Definition list ends without a blank line; unexpected unindent.
  ./lib/list_sort.c:161: WARNING: Unexpected indentation.
  ./lib/list_sort.c:162: WARNING: Block quote ends without a blank line; unexpected unindent.

Fix the offending literal block and make the error go away.

Fixes: 043b3f7b ("lib/list_sort: simplify and remove MAX_LIST_LENGTH_BITS")
Cc: George Spelvin <lkml@sdf.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

lib/list_sort.c

@@ -120,7 +120,8 @@ static void merge_final(void *priv, cmp_func cmp, struct list_head *head,
  * The latter offers a chance to save a few cycles in the comparison
  * (which is used by e.g. plug_ctx_cmp() in block/blk-mq.c).
  *
- * A good way to write a multi-word comparison is
+ * A good way to write a multi-word comparison is::
+ *
  *	if (a->high != b->high)
  *		return a->high > b->high;
  *	if (a->middle != b->middle)