kconfig: allow build-time definition of the internal config prefix

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index 4fb5902..64da30c 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -566,7 +566,7 @@
 
 	if (menu_has_help(menu)) {
 		if (sym->name) {
-			str_printf(help, "CONFIG_%s:\n\n", sym->name);
+			str_printf(help, "%s%s:\n\n", CONFIG_, sym->name);
 			str_append(help, _(menu_get_help(menu)));
 			str_append(help, "\n");
 		}