Revert "sound: Merge chn_intr() with chn_intr_locked()"

It turns out that snd_uaudio(4) uses sound(4)'s channel lock for its USB
transfer callbacks. I will try to address this at some point, because
this is layering violation, but for now we need to revert the commit, as
it causes a lock recursion panic with USB audio devices.

This reverts commit e254ef87a3.

sys/dev/sound/pcm/channel.c

@@ -581,14 +581,30 @@ chn_read(struct pcm_channel *c, struct uio *buf)
 }
 
 void
-chn_intr(struct pcm_channel *c)
+chn_intr_locked(struct pcm_channel *c)
 {
-	CHN_LOCK(c);
+
+	CHN_LOCKASSERT(c);
+
 	c->interrupts++;
+
 	if (c->direction == PCMDIR_PLAY)
 		chn_wrintr(c);
 	else
 		chn_rdintr(c);
+}
+
+void
+chn_intr(struct pcm_channel *c)
+{
+
+	if (CHN_LOCKOWNED(c)) {
+		chn_intr_locked(c);
+		return;
+	}
+
+	CHN_LOCK(c);
+	chn_intr_locked(c);
 	CHN_UNLOCK(c);
 }
 

sys/dev/sound/pcm/channel.h

@@ -298,6 +298,7 @@ int chn_oss_setorder(struct pcm_channel *, unsigned long long *);
 int chn_oss_getmask(struct pcm_channel *, uint32_t *);
 
 void chn_resetbuf(struct pcm_channel *c);
+void chn_intr_locked(struct pcm_channel *c);
 void chn_intr(struct pcm_channel *c);
 int chn_abort(struct pcm_channel *c);