[ALSA] cmipci - allow capture of raw spdif subframes

Enable capturing of raw 32bit IEC958_SUBFRAME.
The 24-bits PCM data can be obtained using iec958 plugin.
Known problem: captured stream may begin with either left or right
subframe. Since the iec958 plugin doesn't decode preamble it may swap
the channels sometime.

Signed-off-by: Timofei Bondarenko <tim@ipi.ac.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>