memcg: make PGPGIN and PGPGOUT v1 only

Currently PGPGIN and PGPGOUT are used and exposed in the memcg v1 only
code.  So, let's put them under CONFIG_MEMCG_V1.

Link: https://lkml.kernel.org/r/20240815050453.1298138-8-shakeel.butt@linux.devSigned-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol.c

@@ -408,8 +408,10 @@ unsigned long lruvec_page_state_local(struct lruvec *lruvec,
 
 /* Subset of vm_event_item to report for memcg event stats */
 static const unsigned int memcg_vm_event_stat[] = {
+#ifdef CONFIG_MEMCG_V1
 	PGPGIN,
 	PGPGOUT,
+#endif
 	PGSCAN_KSWAPD,
 	PGSCAN_DIRECT,
 	PGSCAN_KHUGEPAGED,
@@ -1429,10 +1431,11 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
 		       memcg_events(memcg, PGSTEAL_KHUGEPAGED));
 
 	for (i = 0; i < ARRAY_SIZE(memcg_vm_event_stat); i++) {
+#ifdef CONFIG_MEMCG_V1
 		if (memcg_vm_event_stat[i] == PGPGIN ||
 		    memcg_vm_event_stat[i] == PGPGOUT)
 			continue;
-
+#endif
 		seq_buf_printf(s, "%s %lu\n",
 			       vm_event_name(memcg_vm_event_stat[i]),
 			       memcg_events(memcg, memcg_vm_event_stat[i]));