mm/page_alloc: remove redundant pcp->free_count initialization in per_cpu_pages_init()

mm/page_alloc: remove redundant pcp->free_count initialization in per_cpu_pages_init()

In per_cpu_pages_init(), pcp->free_count is explicitly initialized to 0,
but this is redundant because the entire struct is already zeroed by
memset(pcp, 0, sizeof(*pcp)).

Link: https://lkml.kernel.org/r/20250814071828.12036-1-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>