platform/chrome: cros_ec_proto: return 0 on getting wake mask success

cros_ec_get_host_event_wake_mask() used to return value from
send_command() which is number of bytes for input payload on success
(i.e. sizeof(struct ec_response_host_event_mask)).

However, the callers don't need to know how many bytes are available.

Don't return number of available bytes.  Instead, return 0 on success;
otherwise, negative integers on error.
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-20-tzungbi@kernel.org

drivers/platform/chrome/cros_ec_proto.c

@@ -236,7 +236,7 @@ EXPORT_SYMBOL(cros_ec_check_result);
  *
  * @ec_dev: EC device to call
  * @msg: message structure to use
- * @mask: result when function returns >=0.
+ * @mask: result when function returns 0.
  *
  * LOCKING:
  * the caller has ec_dev->lock mutex, or the caller knows there is
@@ -266,6 +266,7 @@ static int cros_ec_get_host_event_wake_mask(struct cros_ec_device *ec_dev, uint3
 	if (ret > 0) {
 		r = (struct ec_response_host_event_mask *)msg->data;
 		*mask = r->mask;
+		ret = 0;
 	}
 
 exit: