iwlwifi: bump FW API to 57 for AX devices

Start supporting API version 57 for AX devices.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200930191738.f8660d41f62b.Iac1d5b3186e22956cfd000fd9dc5886a79617b78@changeid


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