This commit adds a new functions and some arrangement for PCM restriction.
This arrangement is due to the number of channels which each Dice device has.

I note that minimum number for period becomes 2, instead of 1 because its PCM
functionality has SNDRV_PCM_INFO_BATCH, this means that the driver uses double
(or more) buffering so the minimum number for period should be 2.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>