ALSA: firewire-motu: destroy stream data surely at failure of card initialization

When failing sound card registration after initializing stream data, this
module leaves allocated data in stream data. This commit fixes the bug.

Fixes: 9b2bb4f2 ('ALSA: firewire-motu: add stream management functionality')
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>