object: use more specific property type names

Use the actual unsigned integer type name.

The type name change impacts the following externally visible area:

* vl.c's machine_help_func() puts it in help for -machine NAME,help.

* QMP command qom-list exposes it in ObjectPropertyInfo member @type.

* QMP command device-list-properties exposes it in DevicePropertyInfo
  member @type.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20170607163635.17635-15-marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
