Add qemu and qemuarm to index of devices

Signed-off-by: Grzegorz Gwóźdź <grzegorz.gwozdz@huawei.com>

docs/hardware-support/virtual-boards/index.rst

@@ -14,3 +14,5 @@ This section details the support for virtual targets in |main_project_name|.
   
    qemux86-64
    qemux86
+   qemuarm64
+   qemuarm