ALSA: usb-audio: Don't try to submit URBs after disconnection

ALSA: usb-audio: Don't try to submit URBs after disconnection

USB-audio driver can still submit URBs while the device is being
disconnected, and it may result in spurious error messages like:
  usb 1-2: cannot submit urb (err = -19)
  usb 1-2: Unable to submit urb #0: -19 at snd_usb_queue_pending_output_urbs
  usb 1-2: cannot submit urb 0, error -19: no device
Although those are harmless, they are just ugly.

This patch tries to avoid spewing such error messages when the device
is already at the disconnected state.  It also skips the superfluous
xfer notification, too.

Link: https://lore.kernel.org/r/20230828101924.27107-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>