hw/*/realview: Fix introspection problem with 'realview_mpcore' & 'realview_gic'

hw/*/realview: Fix introspection problem with 'realview_mpcore' & 'realview_gic'

echo "{'execute':'qmp_capabilities'} {'execute':'device-list-properties'," \
 "'arguments':{'typename':'realview_mpcore'}}" \
 "{'execute': 'human-monitor-command', " \
 "'arguments': {'command-line': 'info qtree'}}" | \
 valgrind -q aarch64-softmmu/qemu-system-aarch64 -M none,accel=qtest -qmp stdio
[...]
==2654== Invalid read of size 8
==2654==    at 0x61878A: qdev_print (qdev-monitor.c:686)
==2654==    by 0x61878A: qbus_print (qdev-monitor.c:719)
==2654==    by 0x452B38: handle_hmp_command (monitor.c:3446)
==2654==    by 0x452D70: qmp_human_monitor_command (monitor.c:821)
[...]

Use sysbus_init_child_obj() to fix it.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1531745974-17187-14-git-send-email-thuth@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>