mfd: madera: Add common support for Cirrus Logic Madera codecs

This adds the generic core support for Cirrus Logic "Madera" class codecs.
These are complex audio codec SoCs with a variety of digital and analogue
I/O, onboard audio processing and DSPs, and other features.

These codecs are all based off a common set of hardware IP so can be
supported by a core of common code (with a few minor device-to-device
variations).

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Nikesh Oswal <Nikesh.Oswal@cirrus.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>