ASoC: Intel: Rename Baytrail kernel module and Kconfig symbol

Follows the Haswell naming and lsmod showing snd_soc_sst_baytrail_pcm is
more clear than snd_soc_sst_byt_pcm. Note this doesn't affect existing
config files as SND_SOC_INTEL_BAYTRAIL is not explicitly user selectable
but selected by the machine driver.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>