bearer-mbim: make packet service attach operation optional

Some modems do require it, but some others won't (e.g. CDMA based ones), so
just make the operation optional, but only if the modem replies NoDeviceSupport.

https://bugzilla.gnome.org/show_bug.cgi?id=702419

src/mm-bearer-mbim.c

@@ -548,9 +548,17 @@ packet_service_set_ready (MbimDevice *device,
     }
 
     if (error) {
-        g_simple_async_result_take_error (ctx->result, error);
-        connect_context_complete_and_free (ctx);
-        return;
+        /* Don't make NoDeviceSupport errors fatal; just try to keep on the
+         * connection sequence even with this error. */
+        if (g_error_matches (error, MBIM_STATUS_ERROR, MBIM_STATUS_ERROR_NO_DEVICE_SUPPORT)) {
+            mm_dbg ("Device doesn't support packet service attach");
+            g_error_free (error);
+        } else {
+            /* All other errors are fatal */
+            g_simple_async_result_take_error (ctx->result, error);
+            connect_context_complete_and_free (ctx);
+            return;
+        }
     }
 
     /* Keep on */