mm, swap: no need to clear the shadow explicitly

mm, swap: no need to clear the shadow explicitly

Since we no longer bypass the swap cache, every swap-in will clear the
swap shadow by inserting the folio into the swap table.  The only place we
may seem to need to free the swap shadow is when the swap slots are freed
directly without a folio (swap_put_entries_direct).  But with the swap
table, that is not needed either.  Freeing a slot in the swap table will
set the table entry to NULL, which erases the shadow just fine.

So just delete all explicit shadow clearing, it's no longer needed.  Also,
rearrange the freeing.

Link: https://lkml.kernel.org/r/20260218-swap-table-p3-v3-12-f4e34be021a7@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>