Current implementation uses list of packet descriptor as template to
schedule isochronous packet. The packet descriptors are operated by
position and size, while circular linked list is convenient to enumerate
the packet descriptors.

This commit utilizes circular linked list for the purpose.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230109021738.75543-2-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>