iwlwifi: add new firmware for 135 devcies

http://intellinuxwireless.org/iwlwifi/downloads/iwlwifi-135-ucode-18.168.6.1.tgz

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

WHENCE

@@ -736,9 +736,15 @@ Info: v17.168.5.3
 File: iwlwifi-6000g2b-5.ucode
 Info: v17.168.5.1
 
+File: iwlwifi-135-6.ucode
+Info: v18.168.6.1
+
 File: iwlwifi-100-5.ucode
 Info: v39.31.5.1
 
+File: iwlwifi-105-6.ucode
+Info: v18.168.6.1
+
 Licence: Redistributable. See LICENCE.iwlwifi_firmware for details
 
 Also available from http://intellinuxwireless.org/?n=Downloads