sound: Use sound_register_*() for additional OSS minor devices

Since OSS driver creates the device entries for /dev/audio* and
/dev/dspW* by itself without coping with sound_core, it leads to
conflicts with others and let sysfs spewing warnings.

This patch rewrites the registration part of OSS driver to use
the standard method also for additional minor devices.

Reported-by: Steven Rostedt <rostedt@goodmis.org> (with ktest.pl)
Tested-by: Steven Rostedt <rostedt@goodmis.org> (with ktest.pl)
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/sound_core.c b/sound/sound_core.c
index 5580ace..6ce2778 100644
--- a/sound/sound_core.c
+++ b/sound/sound_core.c
@@ -384,6 +384,9 @@
 	    case 4:
 		name = "audio";
 		break;
+	    case 5:
+		name = "dspW";
+		break;
 	    case 8:
 		name = "sequencer2";
 		if (unit >= SOUND_STEP)