iwlwifi: update firmware for 6205

version 18.168.6.1

This adds support for WoWLAN and P2P, both of
which are still experimental in the driver.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[bwh: Do not remove the previous version]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

WHENCE

@@ -759,6 +759,9 @@ Version: 41.28.5.1
 File: iwlwifi-6000g2a-5.ucode
 Version: 17.168.5.3
 
+File: iwlwifi-6000g2a-6.ucode
+Version: 18.168.6.1
+
 File: iwlwifi-6000g2b-5.ucode
 Version: 17.168.5.1