power: supply: cpcap-charger: Add missing power_supply_config

Otherwise cpcap-battery won't probe properly with the power-supplies
property configured but will fail with "Not all required supplies found,
defer probe".

Cc: Marcel Partap <mpartap@gmx.net>
Cc: Michael Scott <michael.scott@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>