xen/dt: Handle correctly node without interrupt-map in dt_for_each_irq_map

dt_for_each_irq_map() returns error if no irq mapping is found.
With this patch, ignore error and return success

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
Reviewed-by: Julien Grall <julien.grall@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

xen/common/device_tree.c

@@ -1081,11 +1081,11 @@ int dt_for_each_irq_map(const struct dt_device_node *dev,
 
     /* Now look for an interrupt-map */
     imap = dt_get_property(dev, "interrupt-map", &imaplen);
-    /* No interrupt map, check for an interrupt parent */
+    /* No interrupt-map found. Ignore */
     if ( imap == NULL )
     {
         dt_dprintk(" -> no map, ignoring\n");
-        goto fail;
+        return 0;
     }
     imaplen /= sizeof(u32);