mfd: Initial support for Wolfson Arizona platform and WM5102 devices

The Wolfson Arizona platform is used to provide common register
interface to a series of low power audio hub CODECs, starting with the
WM5102. Since the features of these devices work over a range of
subsystems an MFD core driver is provided to instantiate the subdevices
and arbitrate access between them.

As the new regmap wake IRQ functionality is used as part of the driver
it is incorporated as a dependency.