docs: kvm: Fix KVM_KVMCLOCK_CTRL API doc

The KVM_KVMCLOCK_CTRL ioctl signals to supported KVM guests
that the hypervisor has paused it. Update the documentation to
reflect that the guest is notified by this API.

Signed-off-by: Joshua Abraham <sinisterpatrician@gmail.com>
Link: https://lore.kernel.org/r/20200501223624.GA25826@josh-ZenBook


Signed-off-by: Jonathan Corbet <corbet@lwn.net>