sound: fix opensound URL in oss Introduction

Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Documentation/sound/oss/Introduction

@@ -80,7 +80,7 @@ Notes:
     additional features.
 
 2.  The commercial OSS driver may be obtained from the site:
-    http://www/opensound.com.  This may be used for cards that
+    http://www.opensound.com.  This may be used for cards that
     are unsupported by the kernel driver, or may be used
     by other operating systems.