sound: Retire unused CHN_N_* defines

These still haven't been implemented by the original author, and there
doesn't seem to be much use for them anyway.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D56239

sys/dev/sound/pcm/channel.c

@@ -2351,31 +2351,7 @@ chn_notify(struct pcm_channel *c, u_int32_t flags)
 	 */
 	run = (CHN_STARTED(c)) ? 1 : 0;
 	if (run)
-		flags &= CHN_N_VOLUME | CHN_N_TRIGGER;
-
-	if (flags & CHN_N_RATE) {
-		/*
-		 * XXX I'll make good use of this someday.
-		 *     However this is currently being superseded by
-		 *     the availability of CHN_F_VCHAN_DYNAMIC.
-		 */
-	}
-
-	if (flags & CHN_N_FORMAT) {
-		/*
-		 * XXX I'll make good use of this someday.
-		 *     However this is currently being superseded by
-		 *     the availability of CHN_F_VCHAN_DYNAMIC.
-		 */
-	}
-
-	if (flags & CHN_N_VOLUME) {
-		/*
-		 * XXX I'll make good use of this someday, though
-		 *     soft volume control is currently pretty much
-		 *     integrated.
-		 */
-	}
+		flags &= CHN_N_TRIGGER;
 
 	if (flags & CHN_N_BLOCKSIZE) {
 		/*

sys/dev/sound/pcm/channel.h

@@ -405,11 +405,8 @@ enum {
 
 					
 
-#define CHN_N_RATE		0x00000001
-#define CHN_N_FORMAT		0x00000002
-#define CHN_N_VOLUME		0x00000004
-#define CHN_N_BLOCKSIZE		0x00000008
-#define CHN_N_TRIGGER		0x00000010
+#define CHN_N_BLOCKSIZE		0x00000001
+#define CHN_N_TRIGGER		0x00000002
 
 #define CHN_LATENCY_MIN		0
 #define CHN_LATENCY_MAX		10