sound: Remove KASSERT from vchan_setnew()

This check is not really useful, and can in fact break things, if
sysctl_dev_pcm_vchans() calls vchan_setnew() with a value that will not
satisfy the KASSERT condition.

Sponsored by:	The FreeBSD Foundation
MFC after:	2 days
Reviewed by:	dev_submerge.ch, emaste
Differential Revision:	https://reviews.freebsd.org/D46545

(cherry picked from commit 998de46c51)

sys/dev/sound/pcm/vchan.c

@@ -945,9 +945,6 @@ vchan_setnew(struct snddev_info *d, int direction, int newcnt)
 		return (EINVAL);
 
 	if (newcnt > vcnt) {
-		KASSERT((newcnt - 1) == vcnt,
-		    ("bogus vchan_create() request newcnt=%d vcnt=%d",
-		    newcnt, vcnt));
 		/* add new vchans - find a parent channel first */
 		ch = NULL;
 		CHN_FOREACH(c, d, channels.pcm) {