KVM: kvm_stat: do not show halt_wait_ns

Similar to commit 111d0bda ("tools/kvm_stat: Exempt time-based
counters"), we should not show timer values in kvm_stat. Remove the new
halt_wait_ns.

Fixes: 87bcc5fa ("KVM: stats: Add halt_wait_ns stats for all architectures")
Cc: Jing Zhang <jingzhangos@google.com>
Cc: Stefan Raspl <raspl@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Stefan Raspl <raspl@linux.ibm.com>
Message-Id: <20211006121724.4154-1-borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>