Documentation: add --lazy-pages option to page-server description

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

Documentation/criu.txt

@@ -549,6 +549,12 @@ Launches *criu* in page server mode.
 *--port* 'number'::
     Page server port number.
 
+*--lazy-pages*::
+    Serve local memory dump to a remote *lazy-pages* daemon. In this
+    mode the *page-server* reads local memory dump and allows the
+    remote *lazy-pages* deamon to request memory pages in random
+    order.
+
 *lazy-pages*
 ~~~~~~~~~~~~
 Launches *criu* in lazy-pages daemon mode.