Remove redundant assignments.

nchan is overwritten before it is used in all cases.

Index: hdafg.c
===================================================================
RCS file: /cvsroot/src/sys/dev/hdaudio/hdafg.c,v
retrieving revision 1.10
diff -u -p -r1.10 hdafg.c
--- hdafg.c	25 Oct 2016 09:15:55 -0000	1.10
+++ hdafg.c	18 Apr 2017 16:23:23 -0000
@@ -1468,7 +1468,6 @@ hdafg_disable_useless(struct hdafg_softc
 	do {
 		done = 1;
 		/* Disable and mute controls for disabled widgets */
-		i = 0;
 		for (i = 0; i < sc->sc_nctls; i++) {
 			ctl = &sc->sc_ctls[i];
 			if (ctl->ctl_enable == false)
@@ -2790,7 +2789,6 @@ hdafg_assign_mixers(struct hdafg_softc *
 		}
 	}
 	/* Treat unrequired as possible */
-	i = 0;
 	for (i = 0; i < sc->sc_nctls; i++) {
 		ctl = &sc->sc_ctls[i];
 		if (ctl->ctl_audiomask == 0)
@@ -3424,13 +3422,13 @@ hdafg_configure_encodings(struct hdafg_s
 
 	sc->sc_pchan = sc->sc_rchan = 0;
 
-	for (nchan = 0, i = 0; i < sc->sc_nassocs; i++) {
+	for (i = 0; i < sc->sc_nassocs; i++) {
 		nchan = hdafg_assoc_count_channels(sc, &as[i],
 		    HDAUDIO_PINDIR_OUT);
 		if (nchan > sc->sc_pchan)
 			sc->sc_pchan = nchan;
 	}
-	for (nchan = 0, i = 0; i < sc->sc_nassocs; i++) {
+	for (i = 0; i < sc->sc_nassocs; i++) {
 		nchan = hdafg_assoc_count_channels(sc, &as[i],
 		    HDAUDIO_PINDIR_IN);
 		if (nchan > sc->sc_rchan)