ALSA: dice: add proc node for stream formation

Products with DICE interface in market can support variable stream
formats for three levels of sampling transmission frequencies. To
record these formats, a proxy structure got several fields in former
commit.

This commit adds a proc node to output the stream formats for debugging
purpose.

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