usb: typec: Return size of buffer if pd_set operation succeeds

The attribute writing should return the number of bytes used from the
buffer on success.

Fixes: a7cff92 ("usb: typec: USB Power Delivery helpers for ports and partners")
Cc: stable@vger.kernel.org
Signed-off-by: Kyle Tso <kyletso@google.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20240319074309.3306579-1-kyletso@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/class.c

@@ -1310,6 +1310,7 @@ static ssize_t select_usb_power_delivery_store(struct device *dev,
 {
 	struct typec_port *port = to_typec_port(dev);
 	struct usb_power_delivery *pd;
+	int ret;
 
 	if (!port->ops || !port->ops->pd_set)
 		return -EOPNOTSUPP;
@@ -1318,7 +1319,11 @@ static ssize_t select_usb_power_delivery_store(struct device *dev,
 	if (!pd)
 		return -EINVAL;
 
-	return port->ops->pd_set(port, pd);
+	ret = port->ops->pd_set(port, pd);
+	if (ret)
+		return ret;
+
+	return size;
 }
 
 static ssize_t select_usb_power_delivery_show(struct device *dev,