ALSA: oxfw: fix memory leak of discovered stream formats at error path

After finishing discover of stream formats, ALSA OXFW driver has memory
leak of allocated memory object at error path.

This commit releases the memory object at the error path.

Fixes: 6c29230e

 ('ALSA: oxfw: delayed registration of sound card')
Cc: <stable@vger.kernel.org> # v4.7+
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>