iwlwifi: bring up 6000 Series 2x2 AGN Gen2 adapters

This patch is to bring up 6000 Series 2x2 AGN Gen2 adapters.
Seperate various version numbers from 6000 Series definitions;
Add module firmware declaration for the new adapters;
Add additional device IDs and subsystem IDs;

Signed-off-by: Shanyu Zhao <shanyu.zhao@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>