iwlwifi: update firmware for 7260 / 3160 devices

Add new firmware for devices: 7260 and 3160
version:
22.15.8.0

Supported by kernel 3.13 and up.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
UBUNTU: Ubuntu-1.116.2

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