sound(4): Fix some common typos in comments

- s/doens't/doesn't/
- s/apropriate/appropriate/
- s/intepretation/interpretation/

MFC after:	5 days

sys/dev/sound/midi/sequencer.c

@@ -894,7 +894,7 @@ mseq_read(struct cdev *i_dev, struct uio *uio, int ioflag)
 	/*
 	 * I think the semantics are to return as soon
 	 * as possible.
-	 * Second thought, it doens't seem like midimoutain
+	 * Second thought, it doesn't seem like midimoutain
 	 * expects that at all.
 	 * TODO: Look up in some sort of spec
 	 */
@@ -1441,7 +1441,7 @@ mseq_poll(struct cdev *i_dev, int events, struct thread *td)
 
 	ret = 0;
 
-	/* Look up the apropriate queue and select it. */
+	/* Look up the appropriate queue and select it. */
 	if ((events & (POLLOUT | POLLWRNORM)) != 0) {
 		/* Start playing. */
 		scp->playing = 1;

sys/dev/sound/pcm/feeder_chain.c

@@ -652,7 +652,7 @@ feeder_chain(struct pcm_channel *c)
 	}
 
 	/*
-	 * The 'hardware' possibly have different intepretation of channel
+	 * The 'hardware' possibly have different interpretation of channel
 	 * matrixing, so get it first .....
 	 */
 	hwmatrix = CHANNEL_GETMATRIX(c->methods, c->devinfo, hwfmt);

sys/dev/sound/pcm/feeder_matrix.c

@@ -699,7 +699,7 @@ feeder_matrix_compare(struct pcmchan_matrix *m_in, struct pcmchan_matrix *m_out)
 }
 
 /*
- * XXX 4front intepretation of "surround" is ambigous and sort of
+ * XXX 4front interpretation of "surround" is ambigous and sort of
  *     conflicting with "rear"/"back". Map it to "side". Well.. 
  *     who cares?
  */