expo: Fix documentation reference

Fix typo: doc/develop/expo.rst instead of doc/developer/expo.rst

Signed-off-by: Massimo Pegorer <massimo.pegorer+oss@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/boot/expo_build.c b/boot/expo_build.c
index 22f62eb..702bf49 100644
--- a/boot/expo_build.c
+++ b/boot/expo_build.c
@@ -209,7 +209,7 @@
 /**
  * menu_build() - Build a menu and add it to a scene
  *
- * See doc/developer/expo.rst for a description of the format
+ * See doc/develop/expo.rst for a description of the format
  *
  * @info: Build information
  * @node: Node containing the menu description
@@ -282,7 +282,7 @@
 /**
  * menu_build() - Build an expo object and add it to a scene
  *
- * See doc/developer/expo.rst for a description of the format
+ * See doc/develop/expo.rst for a description of the format
  *
  * @info: Build information
  * @node: Node containing the object description
@@ -318,7 +318,7 @@
 /**
  * scene_build() - Build a scene and all its objects
  *
- * See doc/developer/expo.rst for a description of the format
+ * See doc/develop/expo.rst for a description of the format
  *
  * @info: Build information
  * @node: Node containing the scene description