ALSA: oxfw: fix return value in error path of isochronous resources reservation

Even if isochronous resources reservation fails, error code doesn't return
in pcm.hw_params callback.

Cc: <stable@vger.kernel.org> #5.3+
Fixes: 4f380d00

 ("ALSA: oxfw: configure packet format in pcm.hw_params callback")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191209151655.GA8090@workstation
Signed-off-by: Takashi Iwai <tiwai@suse.de>