ALSA: usb-audio: rename substream format field to altset_idx

The snd_usb_substream::format field actually contains the index of the
current alternate setting, so rename it to altset_idx to avoid
confusion.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/proc.c b/sound/usb/proc.c
index be3065e..78fc3ba 100644
--- a/sound/usb/proc.c
+++ b/sound/usb/proc.c
@@ -116,7 +116,7 @@
 		unsigned int i;
 		snd_iprintf(buffer, "  Status: Running\n");
 		snd_iprintf(buffer, "    Interface = %d\n", subs->interface);
-		snd_iprintf(buffer, "    Altset = %d\n", subs->format);
+		snd_iprintf(buffer, "    Altset = %d\n", subs->altset_idx);
 		snd_iprintf(buffer, "    URBs = %d [ ", subs->nurbs);
 		for (i = 0; i < subs->nurbs; i++)
 			snd_iprintf(buffer, "%d ", subs->dataurb[i].packets);