usb: typec: Add partner PD object wrapper

Some port drivers may want to set a Type-C partner as a parent for a
USB Power Delivery object, but the Type-C partner struct isn't exposed
outside of the Type-C class driver. Add a wrapper to
usb_power_delivery_register() which sets the provided Type-C partner
as a parent to the USB PD object. This helps to avoid exposing the
Type-C partner's device struct unnecessarily.

Cc: Benson Leung <bleung@chromium.org>
Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Link: https://lore.kernel.org/r/20221122220538.2991775-2-pmalani@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>