ALSA: pcm: Allow 32 bit sample format in IEC958 channel status helper

Treat 32 bit sample width as if it was 24 bits when generating IEC958
channel status bits. On some platforms 24 sample width is problematic
and to get full 24 bit precision a 32 bit format, using only the 24
most significant bits, may have to be used.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>