ALSA: USB-audio: Break out creation of silent urbs from prepare_outbound_urb()
ALSA: USB-audio: Break out creation of silent urbs from prepare_outbound_urb()

Refactoring in preparation for adding Zoom R16/24 quirk.
No functional change.

Signed-off-by: Ricard Wanderlof <04323e1a54bb826370fcb8140aa3223dab89d18a@axis.com>
Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs