ALSA: dice: use cache of stream format to check running stream

At present, to check running stream, available stream formats are used
at current sampling transmission frequency (stf). But when changing stf,
it's convenient to use cache of stream formats.

This commit applies this idea.

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