gobi: ensure QCDM ports are correctly grabbed

Need to suggest that it's QCDM since the MMPortProbe stuff
doesn't get passed through to mm_base_modem_grab_port() so
we can't detect QCDM ports automatically there.

plugins/mm-plugin-gobi.c

@@ -65,7 +65,9 @@ grab_port (MMPluginBase *base,
     if (!mm_base_modem_grab_port (existing ? existing : modem,
                                   subsys,
                                   name,
-                                  MM_PORT_TYPE_UNKNOWN)) {
+                                  (mm_port_probe_is_qcdm (probe) ?
+                                   MM_PORT_TYPE_QCDM :
+                                   MM_PORT_TYPE_UNKNOWN))) {
         if (modem)
             g_object_unref (modem);
         return NULL;