ASoC: wm_adsp: Add codec_probe and codec_remove stubs

Currently the only init function in wm_adsp is called by the
codec driver early in its probe before the codec has been
registered with SOC.

This patch adds stubs for the codec_probe and codec_remove stages
and calls them from WM5102 and WM5110 codec drivers. This allows us
to hang anything that needs setup during the codec probe stage off
these functions without further modification of the codec drivers.

Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>