ASoC: Intel: tag byt-rt5640 machine driver as deprecated

All the functionality was merged in DPCM-based driver,
keep older driver to avoid breaking userspace but
tag it as unsupported/deprecated

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>