ALSA: usb-audio: Update documentation comment for MS2109 quirk

As the recent fix addressed the channel swap problem more properly,
update the comment as well.

Fixes: 1b7ecc241a ("ALSA: usb-audio: work around streaming quirk for MacroSilicon MS2109")
Signed-off-by: Hector Martin <marcan@marcan.st>
Link: https://lore.kernel.org/r/20200816084431.102151-1-marcan@marcan.st
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/quirks-table.h

@@ -3744,8 +3744,8 @@ ALC1220_VB_DESKTOP(0x26ce, 0x0a01), /* Asrock TRX40 Creator */
  * they pretend to be 96kHz mono as a workaround for stereo being broken
  * by that...
  *
- * They also have swapped L-R channels, but that's for userspace to deal
- * with.
+ * They also have an issue with initial stream alignment that causes the
+ * channels to be swapped and out of phase, which is dealt with in quirks.c.
  */
 {
 	.match_flags = USB_DEVICE_ID_MATCH_DEVICE |