iwlwifi: update PCI Subsystem ID for 1000 series

Update PCI Subsystem ID for 1000 series based on HW SKU. Adding new SKU
for "BG" only devices.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>