ALSA: usb-audio: Remove obsoleted fields in struct snd_usb_substream

The two entries are duplicated in struct snd_usb_endpoint.
Seems forgotten in the last clean-up.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/card.h

@@ -115,8 +115,6 @@ struct snd_usb_substream {
 
 	unsigned int hwptr_done;	/* processed byte position in the buffer */
 	unsigned int transfer_done;		/* processed frames since last period update */
-	unsigned long active_mask;	/* bitmask of active urbs */
-	unsigned long unlink_mask;	/* bitmask of unlinked urbs */
 
 	/* data and sync endpoints for this stream */
 	unsigned int ep_num;		/* the endpoint number */