ASoC: wm_adsp: Pull data through compressed read

Data is read in blocks of up to one fragment is size from the circular
buffer on the DSP and is re-packed to remove the padding byte that
exists in the DSP memory map.

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