ALSA: oxfw: add comment for the type of ASICs

ALSA OXFW supports two types of ASICS; OXFW970 and OXFW971. The former
is known to have a quirk we call 'jumbo payload' that some isochronous
cycles are skipped to transfer isochronous packets during handling
asynchronous transaction. The quirk seems to correspond to firmware
initially delivered by Oxford Semiconductor since the quirk is not
confirmed for Mackie Onyx Satellite in which the revised firmware is
available. The quirk is not confirmed in the latter.

This commit adds code comment to describe the quirk.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210518084557.102681-8-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Iwai <tiwai@suse.de>