ALSA: compress: Add SND_AUDIOCODEC_BESPOKE

When working with the compressed framework occasionally vendors will
use esoteric internal audio formats. For such formats it doesn't really
make sense to add an new define to the kernel as their use is not
sufficiently general.

This patch adds a new define SND_AUDIOCODEC_BESPOKE that vendors can use
in such situations.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>