ims_registrar_pcscf: docs for delete_delay parameter

src/modules/ims_registrar_pcscf/doc/ims_registrar_pcscf_admin.xml

@@ -265,6 +265,25 @@ modparam("ims_registrar_pcscf", "force_icscf_uri", "sip:icscf.mnc001.mcc001.3gpp
         <programlisting format="linespecific">
 ...
 modparam("ims_registrar_pcscf", "reginfo_queue_size_threshold", 42)
+...
+        </programlisting>
+      </example>
+    </section>
+
+    <section>
+      <title><varname>delete_delay</varname> (int)</title>
+
+	  <para>If set greater than 0, the delete of a pcontact record is delayed
+	  with its value instead of being done immediately.</para>
+
+      <para><emphasis>Default value is 0 (delete immediately).</emphasis></para>
+
+      <example>
+        <title><varname>delete_delay</varname> parameter usage</title>
+
+        <programlisting format="linespecific">
+...
+modparam("ims_registrar_pcscf", "delete_delay", 10)
 ...
         </programlisting>
       </example>