staging: vt6655: Fixed C99 // comment errors in wpa.h

The following patch fixes the checkpatch.pl warning:
ERROR: do not use C99 // comments
Signed-off-by: NEsra Altintas <es.altintas@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6655/wpa.h

@@ -80,4 +80,4 @@ WPAb_Is_RSN(
 	PWLAN_IE_RSN_EXT pRSN
 );
 
-#endif // __WPA_H__
+#endif /* __WPA_H__ */