iwlwifi: bump FW API to 61 for AX devices

Start supporting API version 61 for AX devices.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210131201908.99428c76c1fc.I2b075d52119d7e4ced6a044f096ee1589c8e631e@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>