spl: Add a type for the jumper function

This function will be used by the relocating jumper too, so add a
typedef to the header file to avoid mismatches.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/spl.h b/include/spl.h
index 781e5a2..488adbe 100644
--- a/include/spl.h
+++ b/include/spl.h
@@ -292,6 +292,9 @@
 #endif
 };
 
+/* function to jump to an image from SPL */
+typedef void __noreturn (*spl_jump_to_image_t)(struct spl_image_info *);
+
 static inline void *spl_image_fdt_addr(struct spl_image_info *info)
 {
 #if CONFIG_IS_ENABLED(LOAD_FIT) || CONFIG_IS_ENABLED(LOAD_FIT_FULL)