sound: Remove obsolete chn_setvolume()

It is marked as obsolete and there are no consumers of it anymore.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Reviewed by:	markj, emaste
Differential Revision:	https://reviews.freebsd.org/D44853

sys/dev/sound/pcm/channel.c

@@ -1301,19 +1301,6 @@ chn_kill(struct pcm_channel *c)
 	return (0);
 }
 
-/* XXX Obsolete. Use *_matrix() variant instead. */
-int
-chn_setvolume(struct pcm_channel *c, int left, int right)
-{
-	int ret;
-
-	ret = chn_setvolume_matrix(c, SND_VOL_C_MASTER, SND_CHN_T_FL, left);
-	ret |= chn_setvolume_matrix(c, SND_VOL_C_MASTER, SND_CHN_T_FR,
-	    right) << 8;
-
-	return (ret);
-}
-
 int
 chn_setvolume_multi(struct pcm_channel *c, int vc, int left, int right,
     int center)

sys/dev/sound/pcm/channel.h

@@ -265,7 +265,6 @@ int chn_poll(struct pcm_channel *c, int ev, struct thread *td);
 int chn_init(struct pcm_channel *c, void *devinfo, int dir, int direction);
 int chn_kill(struct pcm_channel *c);
 int chn_reset(struct pcm_channel *c, u_int32_t fmt, u_int32_t spd);
-int chn_setvolume(struct pcm_channel *c, int left, int right);
 int chn_setvolume_multi(struct pcm_channel *c, int vc, int left, int right,
     int center);
 int chn_setvolume_matrix(struct pcm_channel *c, int vc, int vt, int val);