wifi: iwlwifi: bump FW API to 78 for AX devices

Start supporting API version 78 for AX devices.

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230417113648.5a4dcbf5a2c1.I125808566fe892ee0865e392bf1b1872daafe8ad@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>