ASoC: Allow user-specified WM8958 multiband compressor configurations

The paramters of the WM8958 multiband compressor can be tuned by the
user for their system using a graphical configuration tool on the host.
Allow the user to specify a set of such paramters in platform data and
select between them at runtime.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>