tls: docs for filtering option for keylog_mode

src/modules/tls/doc/params.xml

@@ -1532,7 +1532,18 @@ verify_client = optional_no_ca
 		<listitem>
 			<para><emphasis>16 (bit 5)</emphasis> - send keys to udp peer</para>
 		</listitem>
+		<listitem>
+			<para><emphasis>1024 (bit 11)</emphasis> - enable filtering of
+			keys logging. When set, filtering is done on: "CLIENT_RANDOM",
+			"CLIENT_HANDSHAKE_TRAFFIC_SECRET", "SERVER_HANDSHAKE_TRAFFIC_SECRET",
+			"EXPORTER_SECRET", "CLIENT_TRAFFIC_SECRET_0", "SERVER_TRAFFIC_SECRET_0"
+			</para>
+		</listitem>
 	</itemizedlist>
+	<para>
+		Bit position is the index starting from 1 (practically a non-zero value
+		is (2 power (bitpos - 1)) ).
+	</para>
 	<para>
 		The default value: 0.
 	</para>