Convert CONFIG_DISABLE_CONSOLE to Kconfig

This converts the following to Kconfig:
   CONFIG_DISABLE_CONSOLE

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
diff --git a/common/Kconfig b/common/Kconfig
index be2e1b8..41f27a1 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -259,6 +259,11 @@
 	  The buffer is allocated immediately after the malloc() region is
 	  ready.
 
+config DISABLE_CONSOLE
+	bool "Add functionality to disable console completely"
+	help
+		Disable console (in & out).
+
 config IDENT_STRING
 	string "Board specific string to be added to uboot version string"
 	help