docs: kvm: add arm/pvtime.rst to index.rst

Add this file to a new kvm/arm index.rst, in order for it to
be shown as part of the virt book.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virt/kvm/arm/index.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+===
+ARM
+===
+
+.. toctree::
+   :maxdepth: 2
+
+   pvtime

Documentation/virt/kvm/index.rst

@@ -10,3 +10,5 @@ KVM
    amd-memory-encryption
    cpuid
    vcpu-requests
+
+   arm/index