ASoC: wm_adsp: Add support for opening a compressed stream

Allow user-space to open a compressed stream, although no data will be
passed yet, as part of this adding the ability to define supported
capabilities per firmware and check these match the stream being opened.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>