[PATCH] sched/fair: Fix ksmd and kthreadd running on isolated CPU0 on arm64 systems

[wujing <realwujing@xxxxxx>]

This bug can be reproduced on Kunpeng arm64 and Phytium arm physical machines,
as well as in virtual machine environments, based on the linux-4.19.y stable
branch:
1. Check the number of CPUs on the system:
   nproc --all
   96

2. Add the parameter isolcpus=0-85 to the grub configuration,
update grub, and reboot.

3. Check the ksmd process:

   ps aux | grep -i ksmd
   root      502  0.0  0.0      0     0 ?        S    10:00   0:00 [ksmd]

   ps -o pid,psr,comm -p 502
   PID PSR COMMAND
   502   0 ksmd

4. Check the kthreadd process:

   ps aux | grep -i kthreadd
   root        2  0.0  0.0      0     0 ?        S    10:00   0:00 [kthreadd]

   ps -o pid,psr,comm -p 2
   PID PSR COMMAND
     2   0 kthreadd