autoboot: Rename CONFIG_MENUKEY to CONFIG_AUTOBOOT_MENUKEY

Since this is part of the autoboot functionality, it makes sense to name
it with an AUTOBOOT prefix. No mainline boards use it so this should be
safe, and downstream boards will need to adjust.

Since this option is just an integer value, it really needs another option
to control whether the feature is enabled or not. Add a new
CONFIG_USE_AUTOBOOT_MENUKEY for that. This fits better with how things are
done with Kconfig, avoiding the need to use a specific value to disable
the feature.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/Kconfig

@@ -153,6 +153,23 @@ config AUTOBOOT_STOP_STR_SHA256
 	  string / password matches a values that is encypted via
 	  a SHA256 hash and saved in the environment.
 
+config AUTOBOOT_USE_MENUKEY
+	bool "Allow a specify key to run a menu from the environment"
+	depends on !AUTOBOOT_KEYED
+	help
+	  If a specific key is pressed to stop autoboot, then the commands in
+	  the environment variable 'menucmd' are executed before boot starts.
+
+config AUTOBOOT_MENUKEY
+	int "ASCII value of boot key to show a menu"
+	default 0
+	depends on AUTOBOOT_USE_MENUKEY
+	help
+	  If this key is pressed to stop autoboot, then the commands in the
+	  environment variable 'menucmd' will be executed before boot starts.
+	  For example, 33 means "!" in ASCII, so pressing ! at boot would take
+	  this action.
+
 endmenu
 
 config BUILD_BIN2C