Rather than implement this as its own case in build_order(), process the
boot_targets environment variable in the bootstd_get_bootdev_order()
function. This allows build_order() to be simplified.

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

Allow a theme to be set. For now this is very simple, just a default font
size to use for all elements.

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

This was a work-around for the fact that global bootmeths such as EFI
bootmgr and VBE don't use a particular bootdev, or at least select it
themselves so that we don't need to scan all bootdevs when using that
bootmeth.

Drop the system bootdev entirely.

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

Now that we can separate this out from the normal bootmeths, update the
code to create it always.

We cannot rely on the device tree to create this, since the EFI project
is quite opposed to having anything in the device tree that helps U-Boot
with its processing.

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

Some boot methods don't act on a single bootdev but instead do their own
thing. An example is EFI bootmgr which scan various devices using its own
logic. Add a bootdev to handle this.

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

Add support for bootflows, including maintaining a list of them and
iterating to find them.

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>

The 'bootstd' device provides the central information about U-Boot
standard boot.

Add a uclass for bootstd and the various helpers needed to make it
work. Also add a binding file.

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