mixer(3): Add HEADNAME to TAILQ_HEAD declarations in man page

Forgot to modify the man page in commit 249526da.

Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D38118

lib/libmixer/mixer.3

@@ -22,7 +22,7 @@
 .\" $FreeBSD$
 .\"
 
-.Dd March 19, 2022
+.Dd January 19, 2023
 .Dt MIXER 3
 .Os
 .Sh NAME
@@ -108,7 +108,7 @@ a simple way.
 A mixer is described by the following structure:
 .Bd -literal
 struct mixer {
-	TAILQ_HEAD(, mix_dev) devs;		/* device list */
+	TAILQ_HEAD(mix_devhead, mix_dev) devs;	/* device list */
 	struct mix_dev *dev;			/* selected device */
 	oss_mixerinfo mi;			/* mixer info */
 	oss_card_info ci;			/* audio card info */
@@ -212,7 +212,7 @@ struct mix_dev {
 		float right;			/* right volume */
 	} vol;
 	int nctl;				/* number of controls */
-	TAILQ_HEAD(, mix_ctl) ctls;		/* control list */
+	TAILQ_HEAD(mix_ctlhead, mix_ctl) ctls;	/* control list */
 	TAILQ_ENTRY(mix_dev) devs;
 };
 .Ed