sound: Remove ncards variable from sound_oss_card_info()

The loop counter is also the card's index, so ncards is redundant.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Reviewed by:	dev_submerge.ch
Differential Revision:	https://reviews.freebsd.org/D45144

(cherry picked from commit 305db91)

Author: christosmarg

sys/dev/sound/pcm/sound.c

@@ -792,17 +792,15 @@ int
 sound_oss_card_info(oss_card_info *si)
 {
 	struct snddev_info *d;
-	int i, ncards;
-
-	ncards = 0;
+	int i;
 
 	for (i = 0; pcm_devclass != NULL &&
 	    i < devclass_get_maxunit(pcm_devclass); i++) {
 		d = devclass_get_softc(pcm_devclass, i);
 		if (!PCM_REGISTERED(d))
 			continue;
 
-		if (ncards++ != si->card)
+		if (i != si->card)
 			continue;
 
 		PCM_UNLOCKASSERT(d);