qom/object_interfaces: Fix QAPI headers included

qom/object_interfaces: Fix QAPI headers included

Since commit a0e61807a3 ("qapi: Remove QMP events and commands from
user-mode builds") we don't generate the "qapi-commands-qom.h"
header in a user-emulation-only build.

Commit f375026606 ("qom: Factor out user_creatable_process_cmdline")
incorrectly added a dependency on this "qapi/qapi-commands-qom.h"
header (the QMP handlers are still defined in qom/qom-qmp-cmds.c).
Remove it, and add "qapi/qmp/qobject.h" which declares qobject_unref.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20221220115709.18508-1-philmd@linaro.org>