s390x: remember the maximum page size

s390x: remember the maximum page size

Let's remember the value (successfully) set via s390_set_max_pagesize().
This will be helpful to reject hotplugged memory devices that would exceed
this initially set page size.

Handle it just like how we handle s390_get_memory_limit(), storing it in
the machine, and moving the handling to machine code.

Message-ID: <20241219144115.2820241-13-david@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>