bootstd: Add the concept of a bootflow

A bootflow encapsulates the process used to boot an operating system.
It typically has a control file (such as extlinux.conf) and information
about which 'bootdev' it came from.

Add the header file for this first, since it is needed by all other
files.

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