iwlwifi: add new PCI IDs for 6000g2 devices

Add new PCI IDs for 6000 Series Gen2 devices
and also defines a new sku of device: 6000g2b 2x2 bgn.

Signed-off-by: Shanyu Zhao <shanyu.zhao@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>