api,dbus: don't return immediate CDMA activation errors

Seems like an unnecessary complication, as the client anyway needs to handle
asynchronously reported errors.

new/org.freedesktop.ModemManager1.Modem.ModemCdma.xml

@@ -23,18 +23,13 @@
     <!--
         Activate:
         @carrier: Name of carrier.
-        @immediate_error: A <link linkend="MMModemCdmaActivationError">MMModemCdmaActivationError</link> value, which is returned for immediate errors. Delayed errors are returned via an #org.freedesktop.ModemManager1.Modem.Cdma::ActivationStateChanged signal.
 
         Provisions the modem for use with a given carrier using the modem's
         <ulink url="http://en.wikipedia.org/wiki/Over-the-air_programming">Over-The-Air (OTA)</ulink>
         activation functionality, if any.
-
-        In the event of immediate failure, returns an error value instead of
-        setting a DBus error.
     -->
     <method name="Activate">
-      <arg name="carrier"         type="s" direction="in"  />
-      <arg name="immediate_error" type="u" direction="out" />
+      <arg name="carrier" type="s" direction="in" />
     </method>
 
     <!--

src/mm-iface-modem-cdma.c

@@ -159,9 +159,7 @@ handle_activate_ready (MMIfaceModemCdma *self,
                                              error);
     else
         mm_gdbus_modem_cdma_complete_activate (ctx->skeleton,
-                                               ctx->invocation,
-                                               MM_MODEM_CDMA_ACTIVATION_ERROR_NONE
-);
+                                               ctx->invocation);
 
     dbus_call_context_free (ctx);
 }