cinterion: bail earlier if the plugin doesn't support the port

Caused a crash with the Sierra plugin due to an assertion failure;
the Cinterion plugin shouldn't claim to possibly support ports
it knows it won't support.  In this case, it claimed to support
Sierra modems, so it would try to run probing after Sierra had
done so.  Ideally this should work, but for now just make sure
the Cinterion plugin doesn't claim to support these ports when
it knows it doesn't.

plugins/mm-plugin-cinterion.c

@@ -123,12 +123,29 @@ supports_port (MMPluginBase *base,
 {
     GUdevDevice *port;
     guint32 cached = 0;
+    const char *subsys, *name;
+    guint16 vendor = 0;
 
     /* Can't do anything with non-serial ports */
     port = mm_plugin_base_supports_task_get_port (task);
     if (strcmp (g_udev_device_get_subsystem (port), "tty"))
         return MM_PLUGIN_SUPPORTS_PORT_UNSUPPORTED;
 
+    /* If we can get the vendor ID from udev then we can short-circuit
+     * the vendor name checks.
+     */
+    subsys = g_udev_device_get_subsystem (port);
+    name = g_udev_device_get_name (port);
+    if (mm_plugin_base_get_device_ids (base, subsys, name, &vendor, NULL)) {
+        /* Vendors: Cinterion (0x1e2d)
+         *          Siemens   (0x0681)
+         * Also including 0 just in case the ports are platform serial ports 
+         * which this plugin does need to check support for.
+         */
+        if (vendor != 0x1e2d && vendor != 0x0681 && vendor != 0)
+            return MM_PLUGIN_SUPPORTS_PORT_UNSUPPORTED;
+    }
+
     /* First thing to check in this plugin is if we got capabilities already.
      * This is because we have a later check of the probed vendor, which is
      * taken also during port probing.