sandbox: exynos: Move CONFIG_CMD_SOUND to Kconfig

Move this over to Kconfig and tidy up.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/Kconfig b/common/Kconfig
index 0a4652b..17930a4 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -339,6 +339,16 @@
 	  getidcr - Get a register value via indirect DCR addressing
 	  setidcr - Set a register value via indirect DCR addressing
 
+config CMD_SOUND
+	bool "sound"
+	depends on SOUND
+	help
+	  This provides basic access to the U-Boot's sound support. The main
+	  feature is to play a beep.
+
+	     sound init   - set up sound system
+	     sound play   - play a sound
+
 endmenu
 
 menu "Boot timing"