ALSA: fireface: register the size of PCM period to AMDTP domain

This commit is a preparation to share the size of PCM period between
PCM substreams on AMDTP streams in the same domain. At this time,
the size of PCM period in PCM substream which starts AMDTP streams in the
same domain is recorded.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191007110532.30270-10-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Iwai <tiwai@suse.de>