qapi/meson: Restrict qdev code to system-mode emulation

Beside a CPU device, user-mode emulation doesn't access
anything else from qdev subsystem.

Tools don't need anything from qdev.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210122204441.2145197-10-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 8d8b0bf..ca74617 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2539,6 +2539,7 @@
 F: qapi/qdev.json
 F: scripts/coccinelle/qom-parent-type.cocci
 F: softmmu/qdev-monitor.c
+F: stubs/qdev.c
 F: qom/
 F: tests/check-qom-interface.c
 F: tests/check-qom-proplist.c