sparc64: Use online cpus instead of present cpus during hotplug.

sparc64: Use online cpus instead of present cpus during hotplug.

As per the hotplug documentation, online cpu maps should be
updated if cpu hotplug happens via sysfs. Thus, all other
cpu maps should be updated basd on the online cpus instead
of present cpus. The following example illustrates the issue
if cpu maps are updated based on present cpus.

Before the fix on a T7-2:

[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu0/topology/thread_siblings_list
0-7
[root@ca-sparc64 hackbench]# echo 0 > /sys/devices/system/cpu/cpu0/online
[root@ca-sparc64 hackbench]# echo 0 > /sys/devices/system/cpu/cpu2/online
[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu1/topology/thread_siblings_list
1,3-7
[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu1/topology/core_siblings_list
1,3-255

[root@ca-sparc64 hackbench]# echo 1 > /sys/devices/system/cpu/cpu2/online
[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu1/topology/core_siblings_list
0-255
[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu1/topology/thread_siblings_list
0-7
This is wrong because cpu0 is still offline.

After the fix:
[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu1/topology/core_siblings_list
1-255
[root@ca-sparc64 hackbench]#
cat /sys/devices/system/cpu/cpu1/topology/thread_siblings_list
1-7

Orabug: 25472256

Signed-off-by: Atish Patra <atish.patra@oracle.com>
Reviewed-by: Chris Hyser <chris.hyser@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>