iwlwifi: mvm: return -ENODATA when reading the temperature with the FW down

It seems that libsensors treats -EIO as a special non-recoverable
failure when it tries to read the temperature while the firmware is
not running.  To solve that, change the error code to a milder
-ENODATA.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=196941

Fixes: c221daf2 ("iwlwifi: mvm: add registration to thermal zone")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/tt.c

@@ -631,7 +631,7 @@ static int iwl_mvm_tzone_get_temp(struct thermal_zone_device *device,
 
 	if (!iwl_mvm_firmware_running(mvm) ||
 	    mvm->fwrt.cur_fw_img != IWL_UCODE_REGULAR) {
-		ret = -EIO;
+		ret = -ENODATA;
 		goto out;
 	}