s390: enable MHP_MEMMAP_ON_MEMORY

Enable MHP_MEMMAP_ON_MEMORY to support "memmap on memory".
memory_hotplug.memmap_on_memory=true kernel parameter should be set in
kernel boot option to enable the feature.

Link: https://lkml.kernel.org/r/20240108132747.3238763-6-sumanthk@linux.ibm.com


Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>