We only want to know whether the folio is anonymous, so use
pfn_swap_entry_folio() and save a call to compound_head().

Link: https://lkml.kernel.org/r/20240111152429.3374566-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>