mm: page_counters: initialize usage using ATOMIC_LONG_INIT() macro

When a page_counter structure is initialized, there is no need to use an
atomic set operation to initialize the usage counter because at this point
the structure is not visible to anybody else.  ATOMIC_LONG_INIT() is what
should be used in such cases.

Link: https://lkml.kernel.org/r/20240726203110.1577216-4-roman.gushchin@linux.dev


Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>