Add a 'fake' go command to the bootm command

For tracing it is useful to run as much of U-Boot as possible so as to get
a complete picture. Quite a bit of work happens in bootm, and we don't want
to have to stop tracing before bootm starts.

Add a way of doing a 'fake' boot of the OS - which does everything up to
the point where U-Boot is about to jump to the OS image. This allows
tracing to record right until the end.

This requires arch support to work.

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

include/image.h

@@ -328,7 +328,8 @@ typedef struct bootm_headers {
 #define	BOOTM_STATE_OS_CMDLINE	(0x00000040)
 #define	BOOTM_STATE_OS_BD_T	(0x00000080)
 #define	BOOTM_STATE_OS_PREP	(0x00000100)
-#define	BOOTM_STATE_OS_GO	(0x00000200)
+#define	BOOTM_STATE_OS_FAKE_GO	(0x00000200)	/* 'Almost' run the OS */
+#define	BOOTM_STATE_OS_GO	(0x00000400)
 	int		state;
 
 #ifdef CONFIG_LMB