sparc64: fix an issue when trying to bring hotplug cpus online

sparc64: fix an issue when trying to bring hotplug cpus online

When booting the kernel with maxcpus= on the command line
and then subsequently trying to bring cpus online using:

echo 1 > /sys/devices/system/cpu/cpu[n]/online

messages of the form:

ldom_startcpu_cpuid: sun4v_cpu_start() gives error 6
Processor[n] is stuck

were being reported on the console.

This commit fixes this issue by ensuring that any cpus not
booted during initial kernel boot are explicitly stopped.
This then allows them to be successfully brought online later
if required.

Orabug: 25667277

Signed-off-by: Dave Aldridge <david.j.aldridge@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Reviewed-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>