If the ordering produces no entries, this is an error. Report it, so that
the caller doesn't try to continue with a NULL bootmeth.
This fixes a crash in the bootflow_iter test when running with the sandbox
'default' device tree, instead of the required 'test' one.
Signed-off-by: Simon Glass <sjg@chromium.org>
A bootmeth is a method of locating an operating system. For now, just
add the uclass itself. Drivers for particular bootmeths are added later.
If no bootmeths devices are included in the devicetree, create them
automatically. This avoids the need for boilerplate in the devicetree
files.
Signed-off-by: Simon Glass <sjg@chromium.org>
