ALSA: oxfw: discontinue MIDI substream for scs1x at transaction failure

With a previous commit, ALSA oxfw driver retries transferring MIDI
messages at transaction failure for scs1x. On the other hand, there're
fatal transaction error. Then, no MIDI messages reach to the unit anymore.
In this case, MIDI substream should be terminated.

This commit stops MIDI transmission after the fatal error occurs.
Unfortunately, unlike ALSA PCM functionality, ALSA rawmidi core has no
feature to discontinue MIDI substream runtime in kernel side, thus this
commit just stops MIDI transmission without notifying it to userspace.

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