bootstd: Add a way to set up a bootflow

Add a function to init a bootflow, to reduce code duplication.

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

include/bootflow.h

@@ -144,6 +144,18 @@ struct bootflow_iter {
 	bool doing_global;
 };
 
+/**
+ * bootflow_init() - Set up a bootflow struct
+ *
+ * The bootflow is zeroed and set to state BOOTFLOWST_BASE
+ *
+ * @bflow: Struct to set up
+ * @bootdev: Bootdev to use
+ * @meth: Bootmeth to use
+ */
+void bootflow_init(struct bootflow *bflow, struct udevice *bootdev,
+		   struct udevice *meth);
+
 /**
  * bootflow_iter_init() - Reset a bootflow iterator
  *