s390/sparsemem: Provide memory_add_physaddr_to_nid() with CONFIG_NUMA

s390/sparsemem: Provide memory_add_physaddr_to_nid() with CONFIG_NUMA

virtio-mem uses memory_add_physaddr_to_nid() to determine the NID to use
for memory it adds.

We currently fallback to the dummy implementation in mm/numa.c with
CONFIG_NUMA, which will end up triggering an undesired pr_info_once():

	Unknown online node for memory at 0x100000000, assuming node 0

On s390, we map all cpus and memory to node 0, so let's add a simple
memory_add_physaddr_to_nid() implementation that does exactly that,
but without complaining.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20241025141453.1210600-8-david@redhat.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>