vbe: Add a command to show the VBE state

Add a VBE comment which shows the current state. Currently this is just
the phases which booted via VBE.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/spl.h b/include/spl.h
index 7286f4b..3eb27de 100644
--- a/include/spl.h
+++ b/include/spl.h
@@ -66,6 +66,8 @@
 	PHASE_SPL,	/* Running in SPL */
 	PHASE_BOARD_F,	/* Running in U-Boot before relocation */
 	PHASE_BOARD_R,	/* Running in U-Boot after relocation */
+
+	PHASE_COUNT,
 };
 
 /**