backends: move dbus-vmstate1.xml to backends/

Although not used by the backend itself, use a common location for
documentation and sharing purposes.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>

tests/qtest/meson.build

@@ -98,7 +98,7 @@ if dbus_daemon.found() and config_host.has_key('GDBUS_CODEGEN')
   #qtests_i386 += ['dbus-vmstate-test']
   dbus_vmstate1 = custom_target('dbus-vmstate description',
                                 output: ['dbus-vmstate1.h', 'dbus-vmstate1.c'],
-                                input: files('dbus-vmstate1.xml'),
+                                input: meson.source_root() / 'backends/dbus-vmstate1.xml',
                                 command: [config_host['GDBUS_CODEGEN'],
                                           '@INPUT@',
                                           '--interface-prefix', 'org.qemu',