ALSA: usb-audio: midi2: Restart output URBs on resume

ALSA: usb-audio: midi2: Restart output URBs on resume

USB MIDI 2.0 suspend saves the endpoint running state, clears it and
kills all endpoint URBs. Resume restores the running state, but only
restarts input endpoints.

For a running output endpoint, this leaves the endpoint marked running
with an empty URB queue. Output transfer progress depends on either the
rawmidi trigger path starting the queue or an output completion refilling
it. After suspend there is no completion left, and output data that
remains queued in the raw UMP or legacy rawmidi buffer can stay stalled
until userspace happens to trigger the stream again.

Restore the saved state with atomic accessors, keep input endpoints
restarted as before, and restart output endpoints that were running before
suspend. Clear the saved suspend state after restoring it.

Fixes: ff49d1df79ae ("ALSA: usb-audio: USB MIDI 2.0 UMP support")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
Link: https://patch.msgid.link/20260504-usb-midi2-output-resume-v1-1-c089cc8ad3c6@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>