ALSA: firewire-motu: suppless consumption for unused element of array in stack

ALSA: firewire-motu: suppless consumption for unused element of array in stack

In MOTU firewire protocol, data block consists of 24 bit data chunks except
for one quadlet for source packet header (SPH). The number of data chunk in
a data block is different between three clock modes; low, middle and high.
When unit supports ADAT on optical interface, the data block includes some
chunks for ADAT channels. These ADAT chunks are unavailable at high mode.

This driver has local functions to calculate the number of ADAT chunks. But
They uses stack for three clock modes. This is useless for higher mode.

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