power: supply: cpcap-charger: Add minimal CPCAP PMIC battery charger

The custom CPCAP PMIC used on Motorola phones such as Droid 4 has a
USB battery charger. It can optionally also have a companion chip that
is used for wireless charging.

The charger on CPCAP also can feed VBUS for the USB host mode. This
can be handled by the existing kernel phy_companion interface.

Cc: devicetree@vger.kernel.org
Cc: Marcel Partap <mpartap@gmx.net>
Cc: Michael Scott <michael.scott@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>