iwlwifi: fw: add default value for iwl_fw_lookup_cmd_ver

iwlwifi: fw: add default value for iwl_fw_lookup_cmd_ver

For new APIs this avoids checking every return if it's
IWL_FW_CMD_VER_UNKNOWN (99) or it's lower than the new API value

Done with spatch:
-iwl_fw_lookup_cmd_ver(E1, E2, E3)
+iwl_fw_lookup_cmd_ver(E1, E2, E3, IWL_FW_CMD_VER_UNKNOWN)

Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200928121852.70bec6eb8008.I6ea78553801d33f7ed10fcd2e4be4ba781fe469a@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>