maple_tree: fix comment typo with corresponding maple_status

In comment of function mas_start(), we list the return value of different
cases.  According to the comment context, tell the maple_status here is
more consistent with others.

Let's correct it with ma_active in the case it's a tree.

Link: https://lkml.kernel.org/r/20240812150925.31551-2-richard.weiyang@gmail.comSigned-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/maple_tree.c

@@ -1347,7 +1347,7 @@ static void mas_node_count(struct ma_state *mas, int count)
  * - If mas->node is an error or not mas_start, return NULL.
  * - If it's an empty tree:     NULL & mas->status == ma_none
  * - If it's a single entry:    The entry & mas->status == ma_root
- * - If it's a tree:            NULL & mas->status == safe root node.
+ * - If it's a tree:            NULL & mas->status == ma_active
  */
 static inline struct maple_enode *mas_start(struct ma_state *mas)
 {