Move to the new style of defining the bus interfaces in separate modules
in order to simplify dependencies.
Signed-off-by: NMark Brown <broonie@linaro.org>

There are some analogue volume controls in page 1 of the register map so
implement support for them now that we can access the registers.
Signed-off-by: NMark Brown <broonie@linaro.org>

The PCM512x devices use a paged register map covering the entire register
range. Implement support for this, mapping pages in at addresses starting
at 0x100 for ease of use (though since the pages are numbered from 0 there
is going to be an off by one when looking at the first byte as a page
number).

Also mark the new registers as accessible with the exception of the
coefficient RAM which is a bit fiddly and may benefit from some extra
handling to linearise the blocks.
Signed-off-by: NMark Brown <broonie@linaro.org>

Since the core now takes const strings for enums we should be constifying
them (and the regulator supplies while we're at it).
Reported-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NMark Brown <broonie@linaro.org>

The PCM512x devices are a family of monolithic CMOS integrated circuits
that include a stereo digital-to-analog converter and additional support
circuitry.

This is an initial driver which supports some core functionality for the
device which covers common use cases but does not cover all features.
Currently only slave clocking modes with automatic clock configuration
are supported and most of the DSP configuration for the device is not
enabled.
Signed-off-by: NMark Brown <broonie@linaro.org>