regulator: cpcap: Add basic regulator support

Many Motorola phones like droid 4 are using a custom PMIC called CPCAP
or 6556002. This PMIC is used with several SoCs, I've noticed at least
omap3, omap4 and Tegra2 based Motorola phones and tablets using it.

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