s390/cpuinfo: add system topology information

This update adjusts /proc/cpuinfo format to meet some user level
programs expectations. It also makes the layout consistent with
x86 where CPU topology is presented as blocks of key-value pairs.

Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>