mm: memcg: make memcg1_update_tree() static

memcg1_update_tree() is not used outside of mm/memcontrol-v1.c anymore,
define it as static and remove the declaration from the header file.

Link: https://lkml.kernel.org/r/20240625005906.106920-12-roman.gushchin@linux.devSigned-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol-v1.c

@@ -201,7 +201,7 @@ static unsigned long soft_limit_excess(struct mem_cgroup *memcg)
 	return excess;
 }
 
-void memcg1_update_tree(struct mem_cgroup *memcg, int nid)
+static void memcg1_update_tree(struct mem_cgroup *memcg, int nid)
 {
 	unsigned long excess;
 	struct mem_cgroup_per_node *mz;

mm/memcontrol-v1.h

@@ -5,7 +5,6 @@
 
 #include <linux/cgroup-defs.h>
 
-void memcg1_update_tree(struct mem_cgroup *memcg, int nid);
 void memcg1_remove_from_trees(struct mem_cgroup *memcg);
 
 static inline void memcg1_soft_limit_reset(struct mem_cgroup *memcg)