[ALSA] usb/caiaq: decrease period_bytes_min

This patch decreases the snd_pcm_hardware->period_bytes_min field in the
caiaq/usb audio driver. The hardware can actually handle as few as 128
bytes, depending on the system. So it makes no sense to keep
applications from actually using such values.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>