common: Rename and move source()

This function has a very generic name which does not adequately describe
its purpose. Rename it and move it to image.h, since it relates to reading
a script from an image.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/image.h b/include/image.h
index 3649644..9c6b6d6 100644
--- a/include/image.h
+++ b/include/image.h
@@ -674,6 +674,18 @@
 		   int arch, int image_type, int bootstage_id,
 		   enum fit_load_op load_op, ulong *datap, ulong *lenp);
 
+/**
+ * image_source_script() - Execute a script
+ *
+ * Executes a U-Boot script at a particular address in memory. The script should
+ * have a header (FIT or legacy) with the script type (IH_TYPE_SCRIPT).
+ *
+ * @addr: Address of script
+ * @fit_uname: FIT subimage name
+ * @return result code (enum command_ret_t)
+ */
+int image_source_script(ulong addr, const char *fit_uname);
+
 #ifndef USE_HOSTCC
 /**
  * fit_get_node_from_config() - Look up an image a FIT by type