ASoC: Move WM2000 to dev_pm_ops

There's a general move to use dev_pm_ops rather than bus specific functions
in order to facilitate work on the PM core. Do this conversion to WM2000.
The driver ought to be updated to work better in a multi-component model
but the mechanical conversion ensures that we avoid blocking PM core work
until that happens.

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