mm: memory_hotplug: remove head variable in do_migrate_range()

mm: memory_hotplug: remove head variable in do_migrate_range()

Patch series "mm: memory_hotplug: improve do_migrate_range()", v2.

Unify hwpoisoned page handling and isolation of HugeTLB/LRU/non-LRU
movable page, also convert to use folios in do_migrate_range().

This patch (of 2):

Directly use a folio for HugeTLB and THP when calculate the next pfn, then
remove unused head variable.

Link: https://lkml.kernel.org/r/20240816090435.888946-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20240816090435.888946-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>