vbe: Record which phases loaded using VBE

We expect VPL and SPL to load using VBE. Add a record of this so we can
check it in U-Boot proper.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/vbe.h b/include/vbe.h
index ece2697..5ede818 100644
--- a/include/vbe.h
+++ b/include/vbe.h
@@ -26,6 +26,15 @@
 };
 
 /**
+ * struct vbe_handoff - information about VBE progress
+ *
+ * @phases: Indicates which phases used the VBE bootmeth (1 << PHASE_...)
+ */
+struct vbe_handoff {
+	u8 phases;
+};
+
+/**
  * vbe_phase() - get current VBE phase
  *
  * Returns: Current VBE phase