cpuidle-haltpoll: fix error comments in arch_haltpoll_disable

The 'arch_haltpoll_disable' is used to disable guest halt poll.
Correct the comments.

Fixes: a1c4423b ("cpuidle-haltpoll: disable host side polling when kvm virtualized")
Signed-off-by: Li Qiang <liq3ea@163.com>
Message-Id: <20200924155800.4939-1-liq3ea@163.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>