power: supply: smb347-charger: Add missing pin control activation

Pin control needs to be activated by setting the enable bit, otherwise
hardware rejects all pin changes. Previously this stayed unnoticed on
Nexus 7 because pin control was enabled by default after rebooting from
downstream kernel, which uses driver that enables the bit and charger
registers are non-volatile until power supply (battery) is disconnected.
Configure the pin control enable bit. This fixes the potentially
never-enabled charging on devices that use pin control.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>