ASoC: soc-core: Allow machine drivers to override compress_type

This patch allows machine drivers to override the compression type
provided by the codec driver.

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