s390/topology: correct allocation of topology information

The data stored by the STSI instruction can be up to a page in size
but the memblock_virt_alloc allocation for tl_info only specifies
16 bytes. The memory after the short allocation is overwritten
every time arch_update_cpu_topology is called.

Fixes: 8c910580 "s390/numa: establish cpu to node mapping early"
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>