typec: tcpm: Represent source supply through power_supply

This commit adds a power_supply class instance to represent a
PD source's voltage and current properties. This provides an
interface for reading these properties from user-space or other
drivers.

For PPS enabled Sources, this also provides write access to set
the current and voltage and allows for swapping between standard
PDO and PPS APDO.

As this represents a superset of the information provided in the
fusb302 driver, the power_supply instance in that code is removed
as part of this change, so reverting the commit titled
'typec: tcpm: Represent source supply through power_supply class'

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>