ALSA: fireface: add proc node to help debugging

Drivers can retrieve the state and configuration of clock by read
transactions.

This commit allows protocol abstraction layer to to dump the
information for debugging, via proc interface.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>