bootm: Create bootm_final() for pre-boot cleanup

There are various functions which announce that booting is imminent and
do related preparation. Most of these are arch-specific.

In practice, most archs do a similar thing. It would be better to
have a common function, with perhaps some events for things that are
really arch- and board-specific.

Create a new bootm_final() function with the common pre-boot steps:
printing the "Starting kernel" message, recording bootstage data,
optionally writing bootstage to the FDT and printing a report, and
removing active devices.

Be careful to avoid using BIT() macros which are not available with host
tools.

Signed-off-by: Simon Glass <simon.glass@canonical.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/bootm.h

@@ -321,4 +321,14 @@ void zimage_dump(struct boot_params *base_ptr, bool show_cmdline);
  */
 int bootm_boot_start(ulong addr, const char *cmdline);
 
+/**
+ * bootm_final() - Announce and do cleanup before boot
+ *
+ * This performs the common pre-boot steps: printing the "Starting kernel"
+ * message, recording bootstage data, and removing active devices.
+ *
+ * @flag: Boot state flags (BOOTM_STATE_OS_FAKE_GO prints a fake-run message)
+ */
+void bootm_final(int flag);
+
 #endif