usb: typec: tps6598x: Export some power supply properties

This allows downstream supplies and userspace to detect
whether external power is supplied.

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Link: https://lore.kernel.org/r/2c8e81d9da9ff05b065f66edba915edd11f74065.1607166657.git.agx@sigxcpu.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>