tests: qemucaps: Add QMP introspection data for qemu 2.6.0 on aarch64 gicv2

Add QMP schema data query for aarch64. The gic capabilities are
unfortunately queried after the QMP schema and thus this patch needs to
undo the temporary removal of the declared support for query-qmp-schema.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>

tests/qemucapabilitiesdata/caps_2.6.0-gicv2.aarch64.xml

@@ -161,6 +161,7 @@
   <flag name='drive-iotune-max-length'/>
   <flag name='ivshmem-plain'/>
   <flag name='ivshmem-doorbell'/>
+  <flag name='query-qmp-schema'/>
   <version>2006000</version>
   <kvmVersion>0</kvmVersion>
   <package></package>