bootstage: Init as early as possible

bootstage: Init as early as possible

At present we don't allow use of bootstage before driver model is running.
This means we cannot time the init of driver model itself.

Now that bootstage requires its own board-specific timer, we can move its
init to earlier in the sequence, both before and after relocation.

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