This is another preliminary patch for USB MIDI 2.0 gadget driver.
Add a new flag, no_process_stream, to snd_ump for suppressing the UMP
Stream message handling in UMP core.

Link: https://lore.kernel.org/r/20230621110241.4751-3-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>