ALSA: firewire-motu: code refactoring for pcm.hw_params/hw_free callbacks

The pairs of pcm.hw_params callbacks and .hw_free callbacks for both
direction have no differences.

This commit unifies the pairs.

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