bootm: Rename do_bootm_states() to bootm_run_states()

Rename the function to bootm_run_states() to better indicate ts
purpose. The 'do_' prefix is used to indicate a command processor,
which this is now not.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>