Add audio and midi devices, per report from Mike Hebel on port-cobalt.

sys/arch/cobalt/conf/majors.cobalt

@@ -1,4 +1,4 @@
-#	$NetBSD: majors.cobalt,v 1.22 2008/06/08 04:05:58 tsutsui Exp $
+#	$NetBSD: majors.cobalt,v 1.23 2008/10/10 16:44:23 tsutsui Exp $
 #
 # Device majors for cobalt
 #
@@ -49,6 +49,9 @@ device-major	ugen		char 43			ugen
 device-major	ucom		char 44			ucom
 device-major	urio		char 45			urio
 device-major	uscanner	char 46			uscanner
+device-major	audio		char 47			audio
+device-major	midi		char 48			midi
+
 device-major	altq		char 77			altq
 
 device-major	nsmb		char 98			nsmb