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: a7cff92f ("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>