s390/numa: remove redundant cpus_with_topology variable

Variable cpus_with_topology is a leftover that became
unneeded once the fake NUMA support has been removed.

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>